Sōsuke Aizen

"The gaze into the sun." - Tite Kubo

is the former captain of the 5th Division in the Gotei 13. He later leaves the Soul Society with his followers, Gin Ichimaru and Kaname Tōsen. His lieutenant was Momo Hinamori. After waging war against Soul Society with an army of Arrancar, Aizen was defeated by Ichigo Kurosaki and then sealed away by Kisuke Urahara, before later being imprisoned for his crimes.

Appearance


Prior to his departure from the Soul Society, he appeared as a mild-featured man with brown scholarly hair enhanced by square glasses. He wore the standard Shinigami uniform with a captain's haori. However, during his ascent to Hueco Mundo, he removed his glasses and swept his hand through his hair, revealing menacing eyes and a very different hairstyle; his hair is now swept back, with a strand hanging down his face. As he had previously revealed to Renji Abarai, the Aizen they all knew never existed and this would seem to be a visual representation of that claim.

In Hueco Mundo, Aizen is first seen wearing Arrancar clothes over his Shihakushō. Afterwards, after Orihime Inoue is taken to Las Noches, Aizen wore full clothing similar in style to the Arrancar.

Aizen's appearance changes again upon his initial defeat by Ichigo Kurosaki. Aizen loses all of the physical changes made by his transformation and returns to the physical form he had prior to transforming.

Personality
Despite his current villainous status and former position of authority, Aizen is a surprisingly polite, soft-spoken intellectual, often addressing his subordinates by their given names. He rarely shows any sign of alarm or distress and often has entire situations planned out well in advance. Whenever confronted, Aizen is casual and uncaring, attempting to draw out a conversation and make small talk, which often infuriates those he is talking to.

Aizen initially appeared to be a very kind, well-respected captain and was looked up to by many, especially his lieutenant Momo Hinamori. However, this was just a mask to disguise his manipulative and very dangerous nature. In truth, he cares very little for his underlings (both past and present), and is willing to use almost everyone around him as pawns to achieve his means. In his own words, Aizen claims to be unaffected by any form of morals or ethics, as he views them as mere restrictions on his potential. He is, therefore, willing to stop at nothing to further his selfish ambitions, including manipulating or killing anyone if he deems it to be necessary. He is fond of long, complicated, and somewhat convoluted plots, and frequently appears to toy with his underlings for amusement. Unlike most of the other Shinigami who appear to have some kind of honor and kindness, including some Espada, Aizen lacks genuine compassion and honor.

During his time as a captain, he was known to like tofu, but he disliked boiled eggs. In his free time, he often read and he also gave a special lecture of calligraphy at the Shinigami Academy, given that he excelled in this branch of arts. This optional course was immensely popular among the Shinigami students, and many of them felt great sorrow at Aizen's sudden departure.

As the commander of his army of Arrancar, Aizen controls his minions either through acquired respect or fear. Ulquiorra Cifer, one of his noticeably loyal subordinates, revealed in a conversation with Orihime Inoue that they are all there to further Aizen's ambitions. For more rowdy individuals like Grimmjow Jaegerjaquez, he keeps them in line through intimidation and mind games. The Arrancar Aisslinger Wernarr also claims that they follow him because he has no fear, something which beings born from fear and despair find inspiring. Other Arrancar occasionally follow him for reasons unique to themselves, such as Szayelaporro Granz, who follows him with the hopes that he will eradicate the world of all non-Hollows.

To date, the equally manipulative Gin Ichimaru is the only person who seems to be able to see through Aizen's manipulation. Ichimaru has also shown that he has some sense of Aizen's emotions and feelings, correctly identifying that Aizen was enjoying the invasion of Ichigo and his friends and their successes within Las Noches, as well as picking-up on the fact that Aizen had registered the arrival of Hinamori in battle of Fake Karakura Town and was surprised by it. By contrast, Kaname Tōsen has shown no such understanding and has fallen victim to one of Aizen's more minor mind games when Aizen off-handedly manipulated him into punishing Grimmjow for him while Aizen himself kept up his appearance of benevolence.

Aizen's true objective was to overthrow the king of the Soul Society. As he and his fellow traitor captains were departing from the Soul Society, he told Jūshirō Ukitake that "no one has stood on the top of the world", not even the gods, but he aspires to "stand on the heavens and end the unbearable vacancy on the world's throne". To do this, he needs the, a tri-pronged golden key that opens a portal to the dimension in which the Soul King resides. While the location of the key is known only to Captain-Commander Yamamoto, Aizen knows how the original was created and how to manufacture another. To do this, 100,000 souls need to be gathered together (which will kill all the entities used) and vaporize a significant portion of the area used in its forging. His sights are therefore set on Karakura Town, which has an unusually large concentration of spirit particles.

According to Kisuke Urahara, since mastering the Hōgyoku, Aizen has become less cautious in battle, noting that before he subdued the device, Aizen would not have allowed him to use level 90 Kidō, Aizen admits that his new powers allow him to let his guard down. Also due to this new-found power, he has developed more of a seemingly arrogant and overconfident attitude, often not even thinking his attacks or defense through any longer like he used to, or even bothering to find out the effects of his opponents' and his own attacks. In his newest form, he has also developed a severe superiority complex, believing he is now above both Shinigami and Hollows. Because of his superior attitude and high intelligence, Aizen is easily enraged when facing something or someone that he doesn't understand; for example, when witnessing Ichigo in his "Final" form, Aizen becomes furious because he is unable to comprehend how a Human has surpassed him.

History
At an unknown point in the past, Aizen became part of 5th Division under Captain Shinji Hirako. He invested himself in the research and creation of the Hōgyoku even before Kisuke Urahara. To this end, he sacrificed hundreds of Shinigami and hundreds of Rukongai citizens who bore Shinigami talents to his own Hōgyoku. But it was not satisfied with this. He is seen standing in a clearing with three other Shinigami who are kneeling before him by Gin Ichimaru. One of the Shinigami hands Aizen the Hōgyoku. Aizen puts the object in a glass and then hands it back to the Shinigami. Aizen and his subordinates leave an unconscious Rangiku Matsumoto a short distance away. Aizen eventually caught his captain's attention, and was promoted to a lieutenant in order for Shinji to watch over him closely. However, Shinji's action only helped further the realization of his plans.

110 years ago, Aizen was seen making his way to the 5th Division living quarters of his captain. He and Shinji had a discussion about style and trends before they made their way to the promotion ceremony being held at the 1st Division headquarters. As they got there, he witnessed Hiyori Sarugaki attack his captain and the two got into a childish argument. He followed behind while the other captains congregated and had a brief discussion on the status of the Gotei 13. Overhearing Shunsui Kyōraku mention that the previous captain of the 12th Division was promoted, Aizen interrupted and asked what Kyōraku meant by it. Aizen initially conjectured that the promotion was to Central 46. However, Shunsui explained that it had nothing to do with the Central 46 and that the previous Squad Captain Hikifune had been accepted into the Zero Division also known as the Royal Guard. Aizen was left surprised at the revelation.

The following night, after Kisuke Urahara's appointment as the new captain of the 12th Division, Shinji had a short talk with him about his new role as captain. While leaving, Shinji asked, "How long do you plan on watching us from over there?" Using his hand, Shinji revealed Aizen concealed behind some form of camouflage. Aizen complimented his captain and asked him when he sensed him there, to which Shinji replied ever since he was in his mother's womb, and ordered Aizen to follow. Aizen noted that won't do at all. Aizen then commented on how scary a person Shinji was, to which Shinji replied that Aizen was the scary one.

The very next night, Aizen saw Gin Ichimaru killing the 3rd seat of their division, and informed him that he was impressed by his skill. Aizen then asked him how he found the fight, to which Gin stated he found it pathetic.

9 years later, Shinji and Aizen were walking around the Seireitei when they came across Urahara, Hiyori, and 3rd Seat Mayuri Kurotsuchi. While Shinji once again engaged in a childish fight and argument with Hiyori, Aizen asked Urahara if he had heard the news to which Urahara told him he hadn't. Shinji proceeded to take up the tale and tell Urahara about the series of strange deaths that had taken place in Rukongai. Shinji also informed him that the 9th Division had been sent to handle the investigation.

With the disappearance of the 9th Division, Captain-Commander Yamamoto called an emergency meeting and assembled a team to investigate. After coming into contact with Hollowfied 9th Division members the investigation team was dispatched by an unseen assailant. Aizen was seen wandering around at night by Captain Shunsui Kyōraku and some other Shinigami on guard, while the investigation team was still out searching.

It was later revealed that the 5th seat of the 9th Division, Kaname Tōsen, was behind the betrayal of the 9th Division, having stabbed Kensei Muguruma in the back and killed Heizō Kasaki, Shinobu Eishima, and Tōdō Izaemon, who had accompanied Kensei. He subsequently subdued the team sent to locate the missing 9th Division members using his Bankai. When Captain Shinji Hirako of the 5th Division, asked him why he betrayed his captain, he was surprised to be answered by his own lieutenant, Aizen, who stated that Tōsen didn't betray anyone and that he is, in fact, very loyal, and he just faithfully followed his orders.

Shinji admits he was not as surprised as he seemed to be, and Aizen asked if he suspected him, stating that he had expected that much from his captain. Shinji then explains how he had known something was dangerous about Aizen and that he couldn't be trusted. It was for those reasons that Shinji chose him to be his lieutenant, so that he could keep an eye on him. Aizen told him that he was grateful, as due to his deep seated doubts he didn't suspect a thing. When Shinji states that he already made it known that he had suspected him, Aizen elaborated stating that he didn't realize that for the whole past month, it wasn't him walking behind him. Aizen proceeded to explain the power of his Zanpakutō, Kyōka Suigetsu. Aizen informs Shinji that if he was as close to Aizen as other captains were to their lieutenants he would have been able to see through it by picking up on subtle differences between Aizen himself and Aizen's double. It was his lack of trust that kept them from getting close and as such, allowed Aizen to fool Shinji. He also explains that he could have always refused to be Shinji's lieutenant, but decided against that action because his captain's skepticism made the position ideal to carry out his plans. Aizen thus laid the blame for Shinji and his comrades' current predicament at the feet of Shinji. Provoked by this, Shinji's anger triggered a speed-up in the Hollowfication process. Aizen thanked him for being so easily provoked and made a note of the observed connection between Hollowfication and agitated emotions.

As he got ready to kill Shinji and the others, Kisuke Urahara and Tessai Tsukabishi arrived to stop Aizen from dispatching his captain. Aizen and Urahara had a brief discussion about what was transpiring, with Aizen acting innocent at first until Urahara notes that the investigation team doesn't have simple injuries, but were in fact going through Hollowfication. Aizen commended Urahara on his deduction and revealed himself to be behind the disappearances in the Rukongai. As Aizen had been engaging in early experiments on Shinigami/Hollow hybrids, which involved using an unknown device to cause spirits to transform into Hollows, he was responsible for turning his former captain and seven other Shinigami into Visored, though Aizen refused to go into any of those details.

Aizen proceeded to leave the scene of the crime with his henchmen, stating that "there's nothing more to do there". To stop them from retreating, Tessai performed the Hadō #88, "Hiryugekizokushintenraiho" spell against them, only to be countered by Aizen using Bakudō #81. "Dankū", allowing them to escape.

Some point after the Hollowfication incident, Aizen became Captain of the 5th Division, and eventually revealed to Gin the secret to avoiding Kyōka Suigetsu's complete hypnosis. He later made Gin his lieutenant. Aizen continued to experiment on Hollows to transform them into Shinigami and he created Hollows that were close to Shinigami, such as Metastacia and Menos Hollows capable of concealing their Reiatsu. While testing out the mentioned breed of Menos, he and Gin saved the then first year academy students Momo Hinamori, Izuru Kira, and Renji Abarai from them. Aizen's interest was then piqued by them. Realizing their potential, Aizen took them all into his division. While the obedient and loyal Kira and Hinamori became the lieutenants of the 3rd and 5th Divisions under Gin and Aizen, respectively, Renji proved to be too rebellious and was transferred to the 11th Division (later transferring to the 6th Division to become that squad's lieutenant).

Gin and Tōsen later became captains of the 3rd and 9th Divisions, respectively, but remained loyal only to Aizen. According to Aizen, even when Hinamori was his lieutenant, he always thought of Gin as his subordinate.

At some point during their captaincy, Aizen, Gin, and Tōsen, secretly visited Baraggan Louisenbairn, King of Hueco Mundo and Lord of Las Noches. He and Baraggan engaged in a light conversation, with the 5th Division captain asking Baraggan to look at his Zanpakutō. He then continued by asking Baraggan if he was happy in his position and if he would join him in a new world where he will be granted more power. Baraggan dismissed this notion, stating that there was no power higher than his. Aizen then released his Shikai and showed Baraggan the decimation of his army, thus subjugating him in turn. This created great enmity between Aizen and Baraggan, who promised to seek the Shinigami's destruction for all eternity.

Sometime after the Hollowfication Incident and during his and Isshin Shiba's time as captains, he, Gin, and Kaname were still working on their Hollowfication experiments, as well as attempting to locate Shinji Hirako's group. He told his co-conspirators to remain patient, reassuring them that everything will go as planned.

Soon after this, Aizen and his two comrades watched the fight between Isshin and one of their Hollow creations on a monitor, with Aizen wondering why Isshin was present there. Tōsen states that he did not report that he was going, with Gin commenting that this could cause them immense trouble. Intrigued by this interesting turn of events, Aizen referred to Isshin's arrival as an unexpected harvest and asked if it was possible for him to watch the battle at a closer distance. Later, when he arrives at the scene of the battle with Gin and Tōsen, the three of them each wearing a Reiatsu-concealing cloak, Aizen cuts down Isshin from behind. After commenting on the quality of Urahara's cloak, as well as how simply kneading Kidō into it will let the wearer blend into the air, Aizen prepares to leave, stating that Isshin won't be able to use Bankai in his current state and that the Hollow Experiment was a failure if a captain could take it out using just Shikai. After Tōsen expresses his desire to call the sample "White", as this was their first experiment created based on a Shinigami's soul, Aizen comments that it's ironic calling the Hollow "White" because of it's inner whiteness while it's outside is completely encased in black. After observing the fight for a time, Aizen and his cohorts notice the involvement of a Quincy in the fight, which surprises the three of them. After Tōsen decides to eliminate her, Aizen quickly stops him from killing her, eagerly stating that they should see what happens next.

Following White's defeat and destruction, Tōsen expresses his shock and frustration at the events, calling it a failure. Aizen calms him down, saying that the results were interesting and also expressing curiosity on how events will further unfold.

Aizen became aware of the existence of Ichigo Kurosaki when he was born. Understanding the significance of his birth, he had decided to aid his development for his plans. To this end, he had Rukia Kuchiki stationed in Karakura Town. He also put into place obstacles that would force Ichigo to grow stronger, including the Hollow that attacked his family and the Menos Grande that appeared when Uryū Ishida used the Hollow bait.

Soul Society arc
When Rukia Kuchiki is brought back to Soul Society with the Hōgyoku concealed within her body, Aizen quickly manipulates everyone into an elaborate conspiracy. Aizen first kills all the members of the Central 46 Chambers and begins moving Rukia's execution date up. He then begins to plant suspicion within Soul Society, initially speaking of the possibility of a conspiracy with Renji Abarai (without explicitly saying he was behind it) and tries to use Gin's intrusion in repelling Ichigo Kurosaki and the Ryoka to orchestrate suspicion among the gathered captains, particularly Tōshirō Hitsugaya, who witnessed the conversation personally. He later uses his Zanpakutō's ability to trick everyone into believing that he has been killed and has Gin leading everyone to believe Gin himself is the murderer.

He also sets up his lieutenant, Hinamori, to believe that he was likely killed by Hitsugaya, her childhood friend, to get her out of the way. Because of the nature of Rukia's sentence and execution method, the Gotei 13 splits into factions and the captains begin to fight among themselves. During the turmoil, Gin executes the overt aspects of the plan, which begins to be revealed when 4th Division Captain Retsu Unohana begins to suspect that there is something wrong with Aizen's supposedly dead body.

Using a camera fly, Aizen watches Hollowfied Ichigo fighting Byakuya Kuchiki from S.R.D.I.. At that moment, Gin approaches him, wondering if Ichigo already undergone Hollowfication. As Ichigo regains control over his body, Gin becomes disappointed, but Aizen tells him that there is nothing to worry about. Aizen also adds everything is going according to his plan, and that it all begins now.

Aizen reveals himself by nearly killing his lieutenant and defeating Hitsugaya. He is, however. suddenly stopped by Unohana, who has figured out something was wrong with his corpse doll, only for Aizen to reveal his corpse doll and disclose to Unohana and her lieutenant Isane Kotetsu the true abilities of his Zanpakutō. This leaves Unohana to deduce the ritual for being affected by the hypnosis, after which Aizen reveals that because of this Kaname Tōsen has always been his subordinate. Aizen then has Gin bring the two of them to Sōkyoku Hill where Tōsen had brought Renji and Rukia to him.

There he gently orders Renji to put Rukia down. As Renji refuses, he comments on Renji's stubbornness, and says that, in deference to Renji's feelings, it is acceptable if he wants to hold on to her, but that he'll have to just leave the arms he's holding her with behind. Aizen then draws his sword and attacks Renji, but Renji is able to draw his sword in time to dodge Aizen's attack leaving only his right arm damaged. Aizen applauds his ability to dodge and expresses happiness with the improvements in his skill since he was one of Aizen's subordinates. Aizen tells Renji that he doesn't want things to be harder, because he finds it difficult to hold back his strength. He states that as Renji's former superior officer that he finds it unbearable for a subordinate to die. As Renji challenges the assertion, and asks Aizen why he killed Hinamori. Aizen explains that it was an act of compassion, seeing as he'd trained Momo so that she could not live without him. Renji says that Aizen is not the captain he knew, and Aizen states that he was the same man, but that neither Renji nor anyone else had realized what he was. As Renji attacks with his Shikai, Aizen blocks it with his bare hand and easily cuts the segments of the blade apart while also cutting up Renji. Since Renji still refuses to give up Rukia, Aizen prepares to kill him, only to be stopped by Ichigo.

Ichigo teams up with Renji, but even after using Renji's strongest attack with his Shikai to create an opening for Ichigo the attack fails. Aizen displays his prowess by effortlessly disposing of them, first by blocking Ichigo's blade with a single finger and nearly cutting him in half. He then begins to drag Rukia off, while explaining his plans to the critically injured but still conscious Ichigo. He critically injures the 7th Division Captain Sajin Komamura with a level 90 Kidō spell as Komamura attacks him. Afterward, Aizen removes the Hōgyoku from Rukia's body by using information from research by Kisuke Urahara hidden in the chambers of Central 46.

Surprised that the procedure didn't kill her, and having no further use for her, he orders Gin to kill Rukia as he prepares to leave. However, Byakuya saves Rukia by taking the blow. Aizen turns around and is about to draw his Zanpakutō in order to finish her himself, but is suddenly blocked by Yoruichi Shihōin. He is threatened with death from Suì-Fēng's Zanpakutō if he so much as moves. He calls Yoruichi a nostalgic face, but he still appears confident. Aizen then notes how not even Yoruichi and Suì-Fēng will be able to come after him while fighting them. Kūkaku Shiba and Jidanbō Ikkanzaka arrive to assist them as Gin is suddenly restrained by Rangiku Matsumoto, prompting him to apologize for being unable to help Aizen. They are suddenly all surrounded by every captain and lieutenant of the Gotei 13 still capable of moving. However, Aizen just smiles and says that it is time. Realizing something is wrong, Yoruichi yells for Suì-Fēng to get away, and runs away herself just in time. Aizen is suddenly bathed in light along with Gin and Tōsen and Genryūsai Shigekuni Yamamoto calls the others off. He explains that Aizen, Tōsen, and Gin were completely untouchable the moment they were covered in that light, called a Negación, a separate world created by Menos Grande when rescuing one of their own, to transport them to Hueco Mundo.

While leaving, Aizen removes his glasses and change his hair style by combing a hand through it. His glasses evaporate into dust. He then proceeds to announce his goal to stand atop of the world in the heavens and take the place of the absent gods, something no one has ever done before. Before finally ascending into the portal created by the Menos arrival, he bids farewell to all of the Shinigami present and then tells Ichigo that he was very interesting for a Human.

Arrancar arc
From there, Aizen changes his clothing style to resemble that of the Arrancar, and begins to create several Arrancar. At some point, he also finds Coyote Starrk and Lilynette Gingerbuck and is impressed with the Arrancar. He asks if the mountains of Hollows were killed by him and Starrk tells him that they just died. He then makes an offer to Starrk to join him as an ally. Starrk believes Aizen to be strong and agrees to join him. He eventually sends Grand Fisher and two other strong-leveled Hollows to the Human World. Grand Fisher is killed by Isshin Kurosaki and the other two are killed by Ryūken Ishida. Isshin and Urahara contemplate that Aizen sent these pseudo-Arrancar to Earth to look for information on Ichigo.

Later, he sends Ulquiorra Cifer and Yammy Llargo to find Ichigo and report on his progress. They almost kill Tatsuki, Chad, and Orihime, and Yammy manages to kill a square radius of people in the park. After the mission is completed, Ulquiorra and Yammy head to a meeting consisting of Aizen and 20 other Arrancar (including fellow Espada members Grimmjow Jaegerjaquez and Tier Harribel). Ulquiorra, who can crush his left eye, uses the dust from it to show what he has seen himself to the others and Aizen. Grimmjow, Shawlong, and Di Roy question Ulquiorra and Yammy on why they just did not kill them as ordered, though Ulquiorra claims that Ichigo does not pose much of a threat to Aizen or the Espada. Grimmjow and his Fracción (Shawlong, Edrad, Nakeem, Yylfordt, and Di Roy) later invade Karakura Town without orders, causing Kaname Tōsen to travel there and bring back Grimmjow (his Fracción were killed during their unauthorized mission) and punishes Grimmjow himself, when Aizen refuses to take action.

Later, after examining Orihime Inoue's powers, Aizen decides to initiate another invasion on Karakura Town, letting Ulquiorra hand-pick the invasion force; though Aizen personally sends Grimmjow as well. Ulquiorra, Grimmjow, Yammy, Luppi, and Wonderweiss Margela go to invade Karakura Town to capture Orihime. . Ulquiorra succeeds in forcing Orihime to join Aizen's side and brings her to Las Noches, where he has her display her power by restoring Grimmjow's amputated left arm, explaining to the Arrancar present that Orihime's powers are rejection, meaning she is able to "reject" anything that has happened. Orihime also restores Grimmjow's Espada tattoo (at Grimmjow's request). Grimmjow immediately kills his replacement, Luppi, with his newly restored arm.

Hueco Mundo arc
Aizen calls the Espada to a meeting and invites them to have some tea. As they are having their tea, Aizen reveals to them the presence of Ichigo, Ishida, and Chad. When the Espada start to dismiss them off-hand, he warns them not to underestimate the trio, revealing to them their exploits in Soul Society and identifying Orihime as the missing member of their little group, whom the others have come to rescue. At this point, Grimmjow begins to leave, stating that he is going to go eradicate the threat in Aizen's name. However, Aizen stops him and resorts to intimidating Grimmjow with his Reiatsu when the latter hesitates to back down, bringing Grimmjow to his knees. He then tells the other Espada to return to their palaces and wait patiently. He also tells them not to be overconfident, but not to be afraid either because as long as they are with him, no one can defeat them.

At some point, Aizen has Orihime brought to his room by Loly Aivirrne and Menoly Mallia. After sending the two Arrancar away, Aizen shows Orihime the Hōgyoku. He asks her to interpret him showing her the Hōgyoku as a sign of his trust in her and asks her to use her power of event rejection to undo some minor damage that has occurred to the Hōgyoku from being repeatedly reawakened.

Following the arrival of Ichigo and company to Las Noches itself, Aizen is brought the news of Dordoni Alessandro Del Socaccio's death by a messenger. Aizen is unsurprised by Dordoni's demise, but expresses surprise that Ichigo struggled against him. He then corners the messenger by catching him in a lie of omission and demands to know from the messenger, who sent the Exequias after Dordoni. The messenger does not answer, but Szayelaporro Granz intervenes and reveals that it was him. Szayelaporro begs Aizen's forgiveness, which Aizen grants him, but as Szayelaporro turns to leave, tells him to make his reports more thorough next time. This shocks Szayelaporro, as Aizen goes on to ask him if the Reiatsu record he obtained from Dordoni will aid in his research. Szayelaporro replies in the affirmative and leaves. Following his departure, Ichimaru, who had been present in with Aizen the entire time, asks Aizen if he is enjoying himself even though his subordinates are losing. Aizen confesses that the emotion he is feeling at the moment is akin to enjoyment.

After the Espada no. 9 through to no. 5 are defeated by Ichigo, his friends and the invading Shinigami Captains, Aizen has Starrk bring Orihime to him. He tells Orihime to smile and tells her to wait where she is while they go and destroy Karakura Town. He orders Tōsen to cast the Tenteikūra spell and using that he reveals to all his true motivation behind the capture of Orihime. By kidnapping her, he inspires Ichigo and his friends to attempt a rescue, thereby depriving Soul Society of a valuable military asset. Furthermore, when four captains assist in her rescue, adding to the three that have already defected, Soul Society is left at half its regular strength. Thus, he and his forces are now ready to mount their challenge and he leaves with Gin, Tōsen, and Espada no. 3 through to no. 1 to invade Karakura Town, leaving Las Noches in the hands of Ulquiorra.

Fake Karakura Town arc
As he leaves to destroy Karakura Town, he seals the portals the intruders used to access Hueco Mundo, effectively stranding them there until his return and leaves Ulquiorra in charge of Las Noches. Though Soul Society is able to substitute the town for an abandoned facsimile, Aizen only muses that he will have to travel to Soul Society to destroy the real town after he and his forces (Ichimaru, Tōsen, the top three Espada, and their Fracción) defeat the remaining captains. Before his group is able to take action, Aizen is trapped in Yamamoto's fire prison with Ichimaru and Tōsen and is unable to fight. Nevertheless, he claims that such action will be unnecessary, for that the power of his Espada alone will be enough to defeat the Gotei 13.

When Hinamori arrives in the Fake Karakura Town to assist Matsumoto, he has a somewhat intrigued look in his eyes upon sensing that his former lieutenant, whom he assumed he killed, was alive. When Gin asks him if anything is wrong, Aizen calmly states that Hinamori's presence won't make any difference.

Hooleer arrives in the Fake Karakura Town alongside Wonderweiss Margela and blows out the fire prison where Yamamoto had encased Aizen, Gin, and Tōsen in. Aizen comments that the smell of death is splendid as he walks free with his two comrades, believing the smell fits the occasion. Everyone is alerted to his presence, which noticeably scares Izuru Kira, who fears that Soul Society may have lost. However, the Visored arrive and after a short battle against a group of Gillians, Shinji Hirako confronts Aizen. Shinji attempts to slash at Aizen, but is then stopped by Kaname Tōsen as Aizen looks on.

As the battle continues and as Baraggan comes close to his death, he launches his blade at Aizen in a desperate attempt to kill the person responsible for him losing his position as King of Hueco Mundo. But his own Respira destroys the axe before it can even reach Aizen, who simply looks away. Both Starrk and Harribel notice this, and the former even comments on the fact that Aizen has nothing to say at the Segunda's passing.

Aizen observes Starrk's defeat as the Primera Espada falls to the ground and subsequently takes notice of the fight between Tier Harribel and Hiyori Sarugaki, Lisa Yadōmaru, and Tōshirō Hitsugaya. He stops the fight between Gin and Shinji, telling Gin that was enough and states that it is time to end this fight. Using Shūnpo, he appears near Harribel's battle, surprising her. He slashes her straight across her torso with his Zanpakutō, dealing her a serious wound. Her face shows surprise as he tells her that it appears that she is not strong enough to fight for him. After this, he tells Gin and Kaname that it's time to go.

Aizen laments to Harribel that after all the trouble he went through gathering the Espada, that he alone would be more powerful than all of them. Harribel looks at him with rage and stabs her sword into his chest, impaling him. Aizen's expression does not change as he says dealing with her is such a pain, surprising Harribel. She then realizes she attacked an illusion and that she has been stabbed in her back in her left shoulder by Aizen. He then tells her he will never let her raise her sword to him again, to which he withdraws his sword as she falls to the city below. Aizen then tells everyone to come at him, calling out the Gotei 13 and the Visored.

Shinji warns the other Visored to not approach Aizen too quickly, but Aizen taunts them and says they already died that night 100 years ago, so they have nothing to fear. This taunt sends Hiyori over the edge and she charges him, only to be bifurcated by Gin Ichimaru.

Shinji goes to her side and stares down Aizen in anger. Aizen comments there is finally life in Shinji’s eyes. Aizen then taunts him and tells him to face him, as he will unsheathe his sword especially for him. Shinji approaches his former lieutenant to engage him in battle. Shinji tells the others to wait for Ichigo to arrive and Aizen asks why he would put his faith in that boy. Shinji simply tells him that he doesn't expect him to understand as he doesn't even trust his own followers. Aizen states that only the weak rely on others. Shinji questions how he can say that with all the followers he has, as he is sure that Aizen has asked them to trust him. Aizen corrects him stating that he is wrong as he never asked them to trust him at all. He told them to come with him, but he has never told them to trust him and in fact has told them to not trust anyone, including himself, though he sadly laments that there are not many strong enough to do that. Aizen further explains that "All creatures want to believe in something bigger them themselves. They cannot live without blind obedience. And to escape the pressure of that trust, those in whom faith is placed in turn look for someone higher them themselves. And then those people in turn look for someone even stronger. That is how all kings are born. That is how all Gods are born. But make no mistake. They all still abide to me. Because from this point onward, you will witness firsthand the power of the god they foolishly placed their faith in. I will become that god they have no choice, but to believe in."

Shinji comments on Aizen drawing his blade. He then asks Aizen if he is scared, but Aizen remains silent. Shinji then states that there is no point in ignoring him, as no matter how strong he is that he still has to be uneasy. He then quotes Aizen's own words from 100 years ago, about how Shinji had never opened up to him. He then tells Aizen that because of that he doesn't have a clue what kind of powers his Zanpakutō has. Shinji states to Aizen that if he thought that his Kyōka Suigetsu was the only Zanpakutō with the ability to absolutely control other people's senses, he was dead wrong. He then releases his Zanpakutō.

The release of Shinji's Shikai prompts Aizen to comment that it's an interesting shape for a katana. Shinji's sword's ability takes effect then, reversing the world around them. Shinji launches into an attack and manages to hit Aizen. However, after another attempt, Aizen figures out the ability and hits Shinji saying that the ability is child's play. Moments later, he looks down as Sajin Komamura yells up at him. Suddenly, the sky begins to crack and Ichigo Kurosaki breaks through, battle ready, right behind Aizen.

Ichigo's attack hits a barrier Aizen had created. Aizen taunts Ichigo, prompting him to attack again, but Aizen merely dodges. Aizen continues his taunts, with Ichigo beginning to waver, but Komamura appears beside him and tells Ichigo not to be disheartened and that provoking his opponents is Aizen's forte. He and the other Shinigami and Visored prepare to help Ichigo fight Aizen while avoiding becoming influenced by his Shikai. As Hitsugaya starts the attack, Aizen mocks to which he responds someone needed to start. Hitsugaya becomes angry and releases his Bankai. As he is engaged by Hitsugaya, Aizen effortlessly dodges every attack made upon him by the young captain.

As he prepares to counterattack, Komamura and Love attack him, but Aizen stops them Komamura releases Bankai, but Aizen cuts through it, slicing off Komamura's arm. Komamura fails again as Rose tries to attack Aizen only to be pulled towards him and slashed, sending him to the ground. Aizen defeats the remaining Visoreds as he calls them “Pseudo Arrancar”.

Suì-Fēng then moves in front of Aizen. After she mocks him, she creates a dozen clones of herself using Shunpo. The clones move in and attack. Hitsugaya encases Aizen in some ice as Shunsui comes out of a shadow to attack him. Hitsugaya then launches into an attack. Aizen glances at him as Hitsugaya rushes at him, noting to himself that Hitsugaya does not plan ahead due to his young age. Just then he notices Shinji holding Sakanade and realizes it is too late to react since he is in the inverted world.

However, the Aizen before the captains' eyes is only an illusion. He had used Kyōka Suigetsu and switched places with Momo. The real Aizen was lying down next to Kira and Iba. Ichigo, being the only one who has not yet seen Aizen's Shikai, sees through the hypnosis and shouts at the captains, causing them to realize the deception. After his illusion is revealed, he walks up from the ground. Kira and Iba, believing that it is Hinamori walking away, try to follow him, but are cut down with a simple slash. Shinji angrily yells at Aizen, asking him when he cast the illusion. Aizen simply asks when they started thinking he was not using Kyōka Suigetsu. Hitsugaya, overcome with anger at being fooled by Aizen into attacking Hinamori, bellows in rage and charges at Aizen, even with Kyōraku warning him to wait. Aizen tells them that they are all completely open and dispatches the four captains with ease.

As Aizen defeats the last of his challengers, Yamamoto draws his attention with a huge pillar of fire. Aizen states that he is too late and missed his chance and that the Gotei 13 will crumble with his defeat. Aizen taunts Yamamoto and the Captain-Commander becomes enraged, but before he can react, he is stabbed through the chest by Aizen. Yamamoto pulls Aizen in as he says that he can tell it is not an illusion. Yamamoto then reveals his Ennetsu Jigoku technique and says everything caught in it will burn. However, a released Wonderweiss Margela appears behind Yamamoto, and sends him crashing to the ground below. Aizen reveals that Wonderweiss was made for the sole purpose of stopping Yamamoto's abilities. Despite this, Yamamoto remains unfazed, quickly switching to hand-to-hand combat, and almost effortlessly defeats Wonderweiss. However, Aizen says that Yamamoto's flames were all stored within Wonderweiss causing Yamamoto to rush to try and stop them. As Aizen approaches, a battered Yamamoto uses Hadō #96, Ittō Kasō.

Ichigo then pounces on the former captain sending him crashing through a nearby building. Ichigo wounds him, but the wound merely closes up. Aizen reveals that he has placed the Hōgyoku in his chest which instinctively heals its master. Aizen compliments Ichigo's Reiatsu, saying that he has grown, just as he had planned, surprising Ichigo. He then lists various important occurrences in Ichigo’s development and claims they all happened as he desired. Aizen explains that he found Ichigo to be the perfect subject for his research. Ichigo says that Aizen must be lying because of what he said in Soul Society, but he states he was lying back then. Aizen begins to say why he thought Ichigo would be perfect, but is interrupted by the arrival of Isshin Kurosaki, who says that Aizen has said too much. Isshin immediately sends Ichigo off in the distance and Aizen comments that that was a smart move. Aizen asks Gin how long he has been watching to which Gin responds he did not see an opportunity to help. Isshin then attacks Aizen and sends him crashing through multiple buildings. Their battle continues as Isshin begins to notice Aizen tiring, to which Aizen responds that he has reached the limit of his Shinigami self and that the Hōgyoku has begun to understand his desires.

He then goes on to say that the Hōgyoku possesses a will of its own and that he only became aware of this after becoming its master. He explains that the true power of the Hōgyoku is not the removal of the boundaries between Shinigami and Hollow, but to capture and materialize the hearts around it. He claims that it has brought about the "miracles" surrounding Ichigo, Rukia, and Kisuke Urahara. He continues to explain that Kisuke misunderstood the nature of the Hōgyoku because the breakdown of the barrier between Shinigami and Hollow was his own desire. He claims that Ichigo, Sado, and Orihime all got their power from the Hōgyoku and explains more about it before being interrupted by Gin knocking Ichigo into a nearby building. As Ichigo talks to Isshin, Gin asks Aizen if he interrupted his speech. Aizen replied that he had reached the end of his speech and his body is enveloped by the Hōgyoku. As he says the Hōgyoku deserves its name, Aizen is interrupted as he is shot from behind by Kisuke Urahara, whom he welcomes onto the battlefield.

Urahara mentions that it has been a long time since last they met and the two banter about Aizen’s fusion with the Hōgyoku. Aizen explains that it is not fusion, saying that he subjugated the Hōgyoku, which Urahara had failed to master. Urahara glares down at Aizen and remarks that it is true he was unable to master it in the past. Aizen questions his statement, saying that he must be unable to admit defeat. He then retracts the question and impales what he believes to be Urahara. Aizen then tells him that he has already forever lost the chance to command the Hōgyoku. Urahara's body then bursts like a balloon as Urahara then appears and uses Bakudō #61 to which Aizen says that he saw the portable Gigai trick in Yammy's report. He admits he let his guard down as he never thought Urahara would use such a petty trick. He then inquires what Urahara will do now that he has been constricted with "this meager Bakudō". Urahara then asks how much it will take before it is not meager and follows up in quick secession with several other Bakudō. Urahara then begins an incantation and Aizen taunts Urahara, but Urahara responds it is too late to stop it and unleashes Hadō #91 Senjū Kōten Taihō. After the smoke explosion dissipates, Urahara remarks that Aizen has truly let down his guard because of his new found power Aizen deals Urahara a few blows and notes that the Hōgyoku has made him invincible and has no need to dodge. Urahara then states that he was not talking about dodging the Kidō, what he meant was that in the past Aizen would never have come into physical contact with him twice without a plan. Aizen is suddenly trapped by spiritual energy cuffs at his wrists. He stares in shock as Urahara explains the nature of the seal as Aizen is enveloped in a pillar of light.

Aizen says that had he not subjugated the Hōgyoku that would have worked. He then says that the Hōgyoku was beyond Urahara’s comprehension and this battle is a waste. Urahara unsheathes his Zanpakutō prompting Aizen to taunt once more. Isshin comes up from behind and he and Urahara engage Aizen, confusing him. Aizen demands to know what is going on as Yoruichi Shihōin attacks him from above. She smashes into his back with great force. Urahara then yells for Yoruichi to move away. Aizen quickly recovers and before Yoruichi can fully dodge his counterattack, he destroys the armor on Yoruichi's left leg. As Aizen emerges from the rubble with his new form severely cracked, he asks them if this all they have as he plans on crushing them. . He then points out that Yoruichi’s armor must be special for her to survive his attack and he plans on destroying that.

Having shattered more of her armor, Aizen watches on as Yoruichi and Kisuke bicker again. When Kisuke asks why he is staring at him, Urahara says Aizen is showing interest again. Aizen reveals that while he is now much stronger, he still finds Kisuke interesting as he is the only one in Soul Society who exceeds his intellect. Unconcerned by Aizen's words, Kisuke attacks Aizen, but Aizen easily blocks it and Yoruichi’s sneak attack. As he is about to counter her, Yoruichi activates her Shunkō and knocks Aizen to the ground, but her next attack is blocked. Kisuke then intervenes and binds him with Benihime and causes a massive explosion, though to no effect. Isshin then attacks Aizen with Getsuga Tenshō. Aizen emerges from Isshin's attack with a large crack down his new form's face, though he is otherwise unharmed. Aizen defeats Isshin, Urahara and Yoruichi and gathers Gin as he heads off towards Soul Society.

As Aizen arrives at the Dangai world with Gin, he notices the approaching Kōtotsu, but makes quick work of it. Aizen asks Gin what he was afraid of, remarking that reason only exists for those that cannot live without it. As the two reach the Dangai's exit, Aizen declares that they would go on to the edge of reason. As they arrive, Aizen notices they are not in Karakura town due to his destroying the Kōtotsu. As they walk, the come into contact with a man who upon getting close to Aizen turns to dust due to his spiritual power. Gin then spots Tatsuki Arisawa and Aizen identifies her as Ichigo's ally. Aizen and Gin approach but Tatsuki and Keigo are able to withstand his power. Keigo runs, but Aizen says they will simply start with Tatsuki.

Suddenly, Don Kanonji hits him with a blast of energy, but Aizen emerges from the smoke unscathed. Kanonji reaches to hit Aizen, but before he can do so, Rangiku arrives. Gin rushes in and says he will take care of her. As he takes her away, Aizen comments that he is an interesting child. Aizen catches up to the Human and is about to kill them when Zennosuke Kurumadani shows up and uses his Shikai's special ability to trap Aizen under rubble. Aizen, however, easily breaks free. As the Humans run away, Gin returns, prompting Aizen to ask him what happened to Matsumoto to which Gin simply states he killed her. Aizen admits he is surprised as he thought Gin had feelings for her. Gin then likens himself to a snake and says he has no feelings.

Gin asks Aizen his plans to which Aizen reveals them. Gin says that it is good as he then places his hand on Aizen's Zanpakutō blade. Gin then throws up his sleeve and releases Kamishini no Yari from under his arm impaling a surprised Aizen through the chest. Gin reveals the one weakness in Aizen’s Zanpakutō. As he bleeds, Aizen tells Gin that he knew that Gin would betray him. Gin reveals the true ability of his sword. Gin then places his hand up to Aizen's chest and activates his technique Kill, Kamishini no Yari. Aizen curses him. Gin then watches as Aizen's chest begins to dissolve from the inside out, leaving a gaping hole with the Hōgyoku floating in the middle.

Aizen’s body continues to erode as Gin grabs the Hōgyoku, but Aizen slaps Gin’s hand. Gin runs off with the Hōgyoku, leaving a slowly dissolving Aizen to fall to the ground. After uttering Gin's name, Aizen yells in rage and a pillar of light surrounds him. Aizen then splits the pillar of light in two to reveal his new winged form. The Hōgyoku in Gin’s hand disappears and rejoins Aizen as Aizen tells Gin that the Hōgyoku is under his control whether it is in his body or not. He appears quickly behind Gin, and as he turns to face his former captain, Aizen cuts him deeply with one swipe of his sword. Aizen recalls his failure with his own Hōgyoku as he finishes Gin and throws him through a building. Rangiku arrives shortly after and goes to Gin's side. As Aizen closes in on them, he is interrupted with the sudden arrival of Ichigo. Aizen says he is disappointed that Ichigo has not evolved. Ichigo interrupts Aizen, saying that he wants to move their fight away from his friends. Thinking that Ichigo cannot harm him, Aizen refuses. Ichigo grabs Aizen and brings him outside Karakura Town, throwing him into the ground. He tells a stunned Aizen that he will finish the fight in an instant.

Aizen comments upon Ichigo's words and theorizes on his power. He taunts Ichigo before they clash, leveling a nearby mountain. Aizen gloats on his power as he notes that he and Ichigo have both reached the peak of their evolutions. Aizen then notes that he understands the dimensions of his Ichigo's evolution and his own are very different. He states that if he so much as wishes it, he can bring himself to crush his sword with a single blow. Aizen attacks, but Ichigo stops it with his bare hand, surprising Aizen. Aizen tells Ichigo not to get so excited and that he will crush Ichigo with Kidō and uses a full incantation of Hadō #90. Kurohitsugi. Aizen proudly gloats at the full power of his Kidō. Ichigo stops the spell though and tells Aizen that he is stronger as he moves to attack.

Aizen moves away in a flash of light and Ichigo taunts him. Suddenly, the diamond on Aizen’s head opens up and he transforms once more. Aizen uses an energy blast that damages Ichigo’s left arm Aizen then uses a circular blast that surrounds his body, but Ichigo stops it with a wave of his sword. As Aizen looks on with shock, Ichigo tells him that he will end the fight with the Final Getsuga Tenshō. Aizen looks on in wonder at the new form Ichigo is taking. Ichigo then explains what the Final Getsuga Tenshō is and its costs. Aizen is amazed that despite this new transformation, he still feels absolutely nothing from him and theorizes that Ichigo may have surpassed him. Aizen becomes enraged and screams at him that such a thing is impossible. Ignoring Aizen's fits of rage, Ichigo unleashes his attack, enveloping the battlefield in darkness.

Ichigo's attack envelops Aizen, severely wounding him. After Aizen crashes into the ground, the Hōgyoku regenerates his wounds. Ichigo goes to finish Aizen, but his powers begin to fade. However, Aizen’s Zanpakutō begins to fade as well. He tries to finish off Ichigo, but an energy spike emerges from his chest before he can do so. Urahara arrives, taking responsibility for the attack and explains that before Aizen achieved complete transformation, he fired that Kidō into his body on the back of another Kidō. Urahara explains it is a seal as he believed Aizen would not be able to be killed. Aizen gloats once more, however, more spikes of energy emerge from Aizen's chest. Aizen then shouts at Urahara, stating that he hates him. He asks why someone of Urahara's intellect allows himself to be controlled by "that thing". Urahara understands that Aizen is referring to the Soul King realizing that he has seen it. He then tells Aizen that without the Soul King's existence, Soul Society would be rent asunder. Aizen retorts that victors must always speak of the way the world should be, not the way it is. Before Aizen can speak anymore, he is sealed within Urahara's Kidō.

Ten days later, Aizen sits bound to a chair by many black bands. He is standing trial under the authority of the judges of the Central 46 Chambers for high treason and a list of many other crimes. They sentence him to 18,800 years in "Muken", the 8th and lowest level of the underground prison. Aizen questions how he is to receive "judgement" from the likes of them, stating he finds it rather comical. A judge silences him, calling him a traitor and warning him not to get cocky just because he is immortal. He then orders Aizen's eye and mouth bound at once and raises his sentence up to 20,000 years.

The Thousand-Year Blood War arc
During the Vandenreich's invasion of Soul Society, Yhwach reveals that Aizen was being held underneath the First Division, where the leader of the Vandenreich offered him a position in their army, only to be refused by the prisoner. Subsequently, Yhwach discovered that during his meeting with Aizen, he managed to alter his perception of time.

Inventions

 * : Aizen has stated that he arrived at the conclusion of the Hōgyoku before Kisuke Urahara, however, it ended in failure. In order to finalize the Hōgyoku, the souls of hundreds upon hundreds of Shinigami and hundreds and hundreds of Rukongai citizens who bore Shinigami potential needed to be sacrificed to it, but it still wasn't satisfied. According to the experimental data, Kisuke Urahara's Hōgyoku was also incomplete. Therefore, Aizen decided to steal that Hōgyoku and present it to his own. Produced as a result of Aizen's Hollowfication research, this Hōgyoku is what gave the Visored their Hollow powers. This process seems to spread as some form of infection through wounds, which only has the desired effects on souls with high-level spiritual energy and not souls with low-level spiritual energy. Those infected experience great sickness and fatigue, until they vomit up a white liquid that forms the beginnings of their Hollow mask, which then proceeds to transform their bodies and warp their minds. Other than that, all that is known is that the process is accelerated by aggressive emotions. The conclusive result turns a Shinigami into a primarily Hollow-like humanoid, which is a highly unstable transformation causing mindlessness and aggression.


 * : This cube, when used on a subject, traps them in an alternate dimension from which there is no escape, however, this assumes it's being used as intended. More powerful Arrancar, namely the Espada themselves, can escape, given enough time.


 * Hollow Research and Development: During his tenure as a Shinigami and after his defection, Aizen spent much time researching Shinigamis and Hollows in order to break down the boundaries between them. Because of this, he was able to create Hollows with Shinigami-like abilities. He created Hollows with the ability to hide their reiatsu like the ones who attacked Renji Abarai, Izuru Kira, and Momo Hinamori during their training, Hollows, like Metastacia, with the ability to shatter a Shinigami's Zanpakutō and fuse with them , and even a Hollow using a Shinigami's soul as a base . However, according to Aizen, these all ended in failures. After his defection, he began using the Hogyoku to create Arrancars with far superior ability than normally occurring Arrancars . Aizen was also able to give Hollow powers to a Shinigami, namely Kaname Tōsen who gained both a Hollow's mask and a Resurrección.

Equipment

 * Reiatsu Concealing Cloak: A cloak created by Urahara which hides the wearer's spiritual pressure. Aizen used this cloak to sneak up and attack Isshin Shiba. By incorporating Kidō into the cloak, Aizen states it allows the wearer to blend in with the air around them, almost completely concealing them from sight.

Powers & Abilities
Genius Intellect: Arguably, the most fearsome trait of Sōsuke Aizen is his tremendous intellect. He is well-versed in the history, strategy, and tactics of Soul Society, and is privy to knowledge unknown to many, such as the existence of the Ōken, as well as the obscure method in which to create one. He has also created several Hollows and Arrancar while avoiding arousing any suspicion from the majority of his fellow Shinigami. For over 110 years, he had been engaging in experiments that involved unique and highly dangerous manipulations of spirit energy and spirit particles, including experiments involving the Hollowfication of Shinigami, something that had never been done before. He has an innate knowledge of the Hōgyoku, rivaling that of its creator, Kisuke Urahara; he even knows how to destroy it. He is able to figure out Shinji Hirako's Shikai ability's true nature and deduce that it produces an optical illusion, allowing him to counter its effect. He effectively deduces the true nature of the Hōgyoku via trial and error of situations that revolve around it.


 * Master Manipulator: He has shown himself to be a very crafty and cunning man since his public betrayal of Soul Society. He is able to deceive and manipulate others around him in different ways for a variety of purposes. For years, he was able to convince everyone around him that he was a kind-hearted man with the best intentions for Soul Society, while performing horrific actions. He has a great talent for analyzing and observing everything in his presence, allowing him to quickly understand a person's pattern of thinking and better manipulate them. He is also a master strategist, capable of formulating well-thought-out plans several steps ahead of others. These plans are incredibly involved and detailed, and are planned out with the long term in mind, making them seem slightly convoluted. His most well known plan spans over 110 years, a great accomplishment which involved moving people around like pieces on a chessboard and making sure they played the role he had planned out for them.   He is masterful when it comes to "plans within plans," such as kidnapping Orihime, allowing him to use her abilities to extend the shelf life of the Hōgyoku, and, after the departure of Gin, Tōsen and himself, trapping the Ryoka and four captains in Hueco Mundo, making it easier for him to accomplish the goal of his first plan; creating the Ōken and gaining access to the Royal Dimension.


 * Master Tactician: He has also shown himself to be a masterful and flexible tactician, capable of adjusting seamlessly to any given combat situation, if not planning out events well in advance. He understands the strengths, weaknesses and mannerisms of his enemies, and creates strategies to achieve victory; this includes modifying an Arrancar for the sole purpose of defeating Yamamoto, a Shinigami whose abilities surpass his own. Though it can be said that the majority of his tactics rely heavily on his Zanpakutō's special ability, there are few tactics better than manipulating all the senses of your opponents, making it easier for one to attack. Despite viewing his power as worlds beyond others, he is highly cautious in battle, placing special protections on himself so as to leave no blind spots.

Kidō Master: Aizen has great proficiency in using Kidō spells. He is skilled enough to use Kidō without the use of their incantation; he used the Black Coffin (ranked 90) spell, and even though he did not control it entirely (utilizing only a third of the spell's original strength), it was sufficient enough to disable fellow Captain Sajin Komamura. He has even used Dankū (ranked 81) to block another Kidō attack by Tessai Tsukabishi, who was captain of the Kidō Corps and logically the most proficient Kidō master in the Soul Society at the time, while Aizen himself was only a lieutenant. He can produce powerful protection spells while in battle.

Immense Strength: He is powerful enough to stop Ichigo's Bankai with just one index finger (albeit Ichigo was already battle-worn from fighting Byakuya Kuchiki) and almost cut him in half with a single swing of his sword. He stopped Renji's Shikai with his bare hand and broke it with one swing, injuring Renji in the process. He was also able to stop Komamura's Shikai with his bare hand, proving his strength was more than enough to combat someone of the same level. Aizen further displays his strength by effortlessly cutting through the sword and wrist of Komamura's Bankai.

Immense Spiritual Power: Even by captain standards, Aizen possesses tremendous spiritual power. Marechiyo Ōmaeda commented that Aizen's very presence is monstrously overwhelming. A hint of his level of spirit power is given when he turns Wonderweiss Margela into an Arrancar before activating the Hōgyoku; he states that despite its half-awakened state, it can be fully activated when temporarily fusing with someone with twice as much spiritual power as an average captain-level Shinigami (referring to himself). The force of Aizen's spiritual power is also great enough to, without any visible effort, bring the 6th Espada to his knees. He has commented that it takes a lot for him not to "crush an ant" (referring to Renji) in his path. He also claims that he is more powerful than all of the Espada. Aizen's Reiatsu is powerful enough to nullify abilities, such as when he negated Suì-Fēng's Nigeki Kessatsu technique. His Reiatsu is violet.

Master Swordsman: While the full extent of his prowess is unknown, Aizen can effortlessly fight back against an opponent's Shikai and Bankai with his own blade still sealed. He can perform tremendously powerful and precise strikes, capable of cutting through very sturdy targets, such as Renji's Shikai. He easily cut down four captains (two which used their Bankai) and four Visored (with three being former captains of Gotei 13) with ease.

Shunpo Master: He is perceived to be so fast that one cannot discern even being attacked by him until after it has taken place. Aizen is shown to easily outmaneuver Ichigo's Bankai and Hollow mask-enhanced speed, to the point where he could casually lay a hand on his chest and still dodge a point-blank attack. He is capable of effortlessly dodging simultaneous attacks at close range and evading Bankai level techniques. He moves so fast that opponents commonly do not know his movements until after he has made them, and is skilled enough in his movements to evade at high speeds, even when being attacked from behind. It's questionable if he is as fast as Yoruichi Shihōin or Suì-Fēng, since they both caught him before he was able to unsheathe his sword to engage in battle before his escape from Soul Society.

Hakuda Master: While preferring to finish his fights quickly with his Zanpakutō or Kidō, Aizen is a highly capable unarmed fighter. Repeatedly, Aizen has effortlessly caught his opponent's weapons with a single bare-hand. While fighting offensively, he has shown tremendous agility and dexterity, able to combine both sword and barehanded skills to simultaneously strike with his sword and kick opponents with great force.

Immortality: After being hit by Ichigo's Mugetsu, he is shown to have somewhat regenerated from the damage, though most of his new form's features have been destroyed and do not return. He is later confirmed by the Central 46 to having been left immortal by his interaction with the Hōgyoku.

Zanpakutō
None. Aizen's Zanpakutō eventually disintegrates, as he claims that the Hōgyoku has determined he no longer needs it.

Former Powers & Abilities
When Kisuke Urahara's Kidō spell, Kyūjūrokkei Kakafūmetsu, begins to seal Aizen, the Hōgyoku rejects him as its master, which leaves him without the powers it granted him.

{{Hidden|Click "show" to read the former powers.
 * content =

Zanpakutō

 * In its sealed form, it resembles a normal katana. The only decoration is the tsuba, which is a hexagon. The two sides parallel to the blade are long, whereas the four sides above and below the blade are shortened, making it into almost a diamond or prism-like shape. It has a green handle.


 * Shikai: The release command is and is used to both activate and deactivate it. The name Kyōka Suigetsu hints at its illusionary properties; the moon reflected in water and a flower in a mirror are things that can be seen, but not held. It is a Chinese saying for seeing and desiring something that is a dream that cannot be easily grasped in hand, teaching people about temptations.


 * Shikai Special Ability: Kyōka Suigetsu's Shikai ability is . It controls the five senses to the point that it can make the target misinterpret another person's form, shape, mass, feel, and smell to be that of the enemy. The initiation condition for the hypnosis is to show the enemy the release of Kyōka Suigetsu. After seeing it just once, that person will completely succumb to the hypnosis. After that, every time it is released, that person will fall under the thrall of the hypnosis. The hypnosis is apparently long-lasting, seeing as the Visored are still affected by Kyōka Suigetsu even though they were hypnotized at least 110 years ago. Since the spell works when you see the ritual, those who cannot see are consequently immune to the hypnosis. When he turns off the hypnosis by force of will, the image shown melts away or shatters. Kyōka Suigetsu's Complete Hypnosis is absolutely flawless; even if the target is aware that they are under the hypnosis, they cannot resist its influence. Kyōka Suigetsu's hypnotic abilities make it a highly useful tool in combat, as Aizen can quickly create simple or complex illusions to deceive his opponents. For example, by creating a decoy of himself, or other illusions to distract his opponents, Aizen can hide his own movements and attack with impunity. His opponent will remain focused on the illusion until it's too late to react.
 * While the illusions Kyōka Suigetsu creates are quite powerful, those with considerable power and skill themselves may be able to note slight differences in the illusions compared to the real thing, even if they are not able to determine what exactly is different. Captain Retsu Unohana was able to detect something was amiss with Aizen's fake corpse, even though she did not realize what until seeing Aizen alive. Kyōka Suigetsu's Reiatsu gives it away to those keen enough to sense its actual presence past the illusions created by its complete hypnosis. The sole way to escape Kyōka Suigetsu's ability is to touch the blade itself before complete hypnosis is activated.


 * Bankai: Not Revealed.

Fusions

 * Aizen embeds the Hōgyoku into the center of his chest.


 * Protective Regeneration: By embedding the Hōgyoku into his chest, it actively protects Aizen by healing his injuries almost instantly. Aizen was able to take a point-blank level 96 destruction spell and only suffer slight burns. Immediately afterwards, he took a point-blank Hollow mask-enhanced black Getsuga Tenshō and survived the attack. He emerged unfazed after being hurled into several buildings.


 * Strength Augmentation: Aizen's already considerable strength is further enhanced by the Hogyoku's evolution of his body. He is able to easily strike through a target's flesh with a single, nonchalant sweep of his bare hands.


 * Durability Augmentation: Aizen's durability is further enhanced by the Hōgyoku's evolution of his body. Because of this, he can withstand a level 91 destruction spell without suffering any damage.


 * After Urahara attempts to block the Reiatsu vents in his wrists with a seal, Aizen emerges from the resulting explosion unscathed as a phantom-like figure. His face is covered with a white canvas, and his outfit is now a white cloak that is split in four sections near his waist. There is a cross in the middle of the cloak, showing where the Hōgyoku is embedded in him. After a short struggle with Yoruichi Shihōin, his Zanpakutō becomes fused to his arm. Also, when he is attacked, his body appears to crack and fold under damage, only actually bleeding when an attack is powerful enough.


 * Enhanced Durability: His durability is great enough to block Isshin's Zanpakutō with just his foot and withstand a massive punch from an armored Yoruichi.


 * Enhanced Endurance: He performs in battle as if he were unharmed, even while taking a lot of damage. He takes on Isshin's point-blank Getsuga Tenshō and remains unfazed by the attack, despite having a bleeding gash on his forehead.


 * Enhanced Strength: Aizen was able to create a shockwave after being knocked down by Yoruichi. This shockwave was fast and strong enough to catch even Yoruichi off guard, and subsequently destroy the Anti-Hierro armor on her left leg.


 * Enhanced Speed: Aizen's new-found power enhances his speed to the point that even captain-level opponents cannot register his movements. He was able to catch the likes of Yoruichi Shihōin off guard. He can incapacitate three captain-level opponents seemingly instantaneously.


 * Regeneration: Aizen also demonstrates a form of regeneration, as seen when he recovers from Yoruichi's first attack.


 * Enhanced Spiritual Power: After Aizen fuses with the Hōgyoku, both Shinigami and Humans are incapable of sensing his Reiatsu unless he voluntarily lowers his level and allows them to interfere. He compares this to how a two-dimensional being is incapable of interfering with a three-dimensional one. Isshin Kurosaki surmised that Aizen's spiritual power can only be sensed by someone that is at the same level as him.


 * After completing his "chrysalis" stage, Aizen shed his sleek phantom-like form to reveal a form similar to his original one, with the addition of long hair and gray eyes with purple sclera. The exact difference in power between his new form and his previous form is unknown.


 * Enhanced Durability: Aizen's durability has been further enhanced. He willingly lets the Kōtotsu collide with him, destroying it, while remaining unharmed.


 * Enhanced Spiritual Power: Aizen's already enormous spiritual energy is further enhanced. By just standing a couple feet away from a Human soul, he causes it to collapse and fade away. By his own claim, if Don Kanonji had come into contact with Aizen, the former would have ceased to exist. Just by touching Gin Ichimaru's arm, his spiritual power caused the area touched to dissolve.


 * After having a hole opened up in his chest by Gin's Kamishini no Yari, spiritual energy erupts from his chest, and Aizen emerges from the blast in this new form. In this form, he has a hole in the center of his chest, with a cross in the middle of it. The form-fitting white robe that enveloped him in his past two forms lengthens, and flares out at the ends. In this form, his irises vanish, as well as his eyebrows and the hair curl that usually hangs over his face. There appears to be a diamond-shaped object embedded in his forehead. He has also gained three sets of butterfly-like wings. When he faces Ichigo, his wings become more pointed, rather than rounded.


 * Regeneration: He is able to regenerate wounds upon his physical form in a matter of minutes.


 * Enhanced Strength: In this form, he is able to effortlessly attack his opponent with minor movement or force. He was able to throw Gin through a nearby building with ease. He caused the ground to tear open with the sheer force of his sword swing, even when the blow was blocked.


 * Teleportation: In this form, he is capable of de-materializing himself from one place and re-materializing himself a distance away. He breaks down his body into multiple purple shards and reassembles himself. (Unnamed)


 * After Aizen is struck by Ichigo Kurosaki, the Hōgyoku forces another transformation upon him, which Aizen claims is because it "doesn't want [him] to lose to a mere human." In this form, Aizen takes on a distinctively Hollow-like form. The diamond shaped point breaks open, revealing a vertical black third eye upon the center of the forehead, and the skin on his face splits open down the middle and pulls back around the sides of his head to reveal a blackened, demon-like skull. He develops three holes running vertically down his chest, the Hōgyoku standing at the center of the top hole. His feet become single claws, and his hands becomes blackened, with his right hand fusing with his Zanpakutō. His butterfly-like wings change into a set of six sheet-like wings, with eyes set upon the center, adorned with Hollow-like skulls, and trailing into tendrils. Aizen no longer has any semblance of clothing in this form, and his musculature becomes more defined.


 * He is able to release bluish-purple energy spheres from the Hollow-like skulls on the top of his wings. One blast is powerful enough to create a large crater, with an accompanying explosion that creates a fallout that can be felt miles away from the blast site.

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 * He surrounds his target with his wings and uses the Hollow-like skulls atop his wings to generate a circle of bluish-purple spiritual energy around a target. Upon creation, the ring reverberates with power and solidifies, while forming three more larger solid rings in concentric formation.

Appearances in Other Media
Aizen is an unlockable character in the Bleach video games. Being the central antagonist, most games have him as the final boss, such as in Bleach: Soul Carnival. His Kurohitsugi Kidō spell is one of his best attacks. In Bleach: Versus Crusade, Bleach: The 3rd Phantom, Bleach: The Blade of Fate and Bleach: Dark Souls, he is also capable of using other Kidō spells, such as Sōkatsui and Rikujōkōrō. He also makes use of his Zanpakutō's abilities throughout most of the games. He makes no appearance or reference in the films; though, in the second OVA, he is seen drinking coffee at the very end with Gin and Tōsen. He also has his own Bleach Beat Collection, Hanabira and Kyōka Suigetsu. In Bleach: Soul Resurrección, he appears only in his First, Second and Fourth transformations, but only playable in his Second Form. In his forms, he can use Kidō and is the final boss in the game. Aizen also appears in the Rock Musical Bleach shows; his actor is Kengo Ohkuchi.

Reception
IGN.com praises the animators for how Aizen was revealed as the primary antagonist saying that "The Aizen that we first knew was the nicest guy ever, he looked it, and now this Aizen actually looks like the most evil jerk we've ever seen. It's just great how the animators haven't changed his animation much, but have managed to give his face this evil thing about it." However, they were critical of Aizen's convoluted plan, calling it "...so planned out was a bit too planned out to believe. He seemed to know that everything was going to happen exactly as planned...." Concerning his Zanpakutō, IGN described it as overpowered, calling it "the most unbalanced sword in Bleach." The site found it "far-fetched for some reason to think that nobody can tell when they're getting hypnotized, even the higher ups."

Trivia

 * Aizen's Kyōka Suigetsu came 18th in the Zanpakutō popularity poll. He himself came 23rd in the 4th, the latest, character popularity poll.
 * Aizen had a column in the Seireitei Communication titled The Yin of the Pine Needle which is now suspended.
 * The Shinigami Women's Association published a Photo Collection showcasing Aizen named The Smile of the Sun but it was cancelled.
 * Aizen's theme song, as chosen by Tite Kubo, is "Stand Ablaze" by In Flames.

Quotes

 * (To Tōshirō Hitsugaya) "You should learn this well, Hitsugaya-kun. Admiration is the emotion furthest from understanding."


 * (To Renji Abarai) "The Sōsuke Aizen you knew...never existed to begin with."


 * (To Jūshirō Ukitake) "No one stands on the top of the world. Not you, not me, not even gods. But the unbearable vacancy of the throne in the sky is over. From now on...I will be sitting on it."


 * (To Shinji Hirako) "The betrayal you can see is trivial. What is truly fearsome, is the betrayal that you don't see, Captain Hirako."


 * (To Tier Harribel indirectly) "I never would've imagined that the power of the Espada I so painstakingly assembled would be less than mine alone."


 * (To Shinji Hirako) "Trusting in someone is the same as depending on them. That is something the weak do. We have no use for it."


 * (To Shinji Hirako) "All living creatures place their faith in someone more powerful than them and they cannot survive unless they blindly follow that person. The recipient of that faith then seeks out someone in an even higher position in order to escape from the pressure. That person then seeks out someone even more powerful that he must put his faith in. In this way all kings are born and in this way all Gods are born. Do not believe in me yet, Hirako Shinji for now I shall slowly teach you who the God is that you will put your faith in. Believing in me comes after that."


 * (To Ichigo Kurosaki) "Why are you putting so much distance between us? If you want to make sure it hits me, then you should get close and fire. Or is it that you're afraid of letting even a part of me out of your field of vision by getting close? If that's the case, then it's a foolish thought. Distance only has meaning in a fight between equals. With you and I, distance holds no meaning at all. Watch... If I do this, my hand is almost instantly at your heart."


 * (To Sajin Komamura) "You thought you could destroy me by striking with power? How naive. ...no perhaps we differ in our basic understandings of the word "power". I shall enlighten you. This is what is known as "power"."


 * "I will not take your lives. With the measure of power that you possess you are unlikely even to lose consciousness from those wounds. Stay there, helpless and defeated and observe carefully as this battle reaches its conclusion."


 * (To Genryūsai Shigekuni Yamamoto) "Your Ryūjin Jakka is indeed the most powerful Zanpakutō in existence. There is no doubt about that. Were I to fight against it directly, it would likely overpower even me. However, if one abandons all other abilities and focuses his strength entirely on a single specialized skill, then he can overcome even the greatest of powers."


 * (To Genryūsai Shigekuni Yamamoto) "Cruel? A soul that's become a Hollow has no purpose. It does nothing more than meaninglessly hunt down souls to prey on. What is so cruel about granting meaning to such an existence? I would say that you're the one who's cruel for smashing that soul to pieces."


 * (To Genryūsai Shigekuni Yamamoto) "To you, I will not say "I will not kill you". You who are the very history of Soul Society itself and as such, you alone will die by my sword."


 * (To Ichigo Kurosaki) "I suppose it is only to be expected. You have my pity. There is no such thing as 'truth' or 'lies' in this world; there never has been. There is only plain, hard facts. And yet, all beings who exist in this world take only those 'facts' that are convenient to them, and take them to be the 'truth'. They do so because they know no other way to live. However, for those powerless beings that make up the majority of this world it is those 'facts' that are inconvenient for their own self-affirmation that make up the real 'truth'."


 * (To Isshin Kurosaki) "...But living creatures are strange. They are made in such a way that they can actualize only what their minuscule minds wish for."


 * (To Kisuke Urahara) "Allow me to be careless, as I don't have the need not to be. I can feel the strength of the Hōgyoku in my body. My strength exceeds my older self. I'm now invincible so I don't have the need to dodge a level 90 Kidō anymore."


 * (To Gin Ichimaru) "Reason exists for those who cannot go on living without clinging to it. Now let's go... to the edge of reason."


 * (To Gin Ichimaru) "Fear is necessary for evolution. The fear that one could be destroyed at any moment. Thank you, Gin. Thanks to your efforts, I have finally risen to an existence that surpasses both Shinigami and Hollow."


 * (To Kisuke Urahara) "That is the theory of the vanquished! Victors must always speak of the way the world should be, not the way it is!"

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