Sōsuke Aizen

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

Appearance
When he was a member of the Gotei 13, Aizen appeared as a mild-featured man with brown scholarly hair enhanced by square glasses, along with soft brown eyes. He wore the standard Shinigami uniform with a captain's haori. 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.

In Hueco Mundo, Aizen initially wears Arrancar style-clothes over his shihakushō. After Orihime Inoue is taken to Las Noches, Aizen wears full clothing similar in style to the Arrancar, complete with a pink sash around the waist.

Upon his 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. While imprisoned in Muken, he wears an almost entirely black outfit with white trimming, a large black eyepatch over his right eye and black boots. A tattered white rag is wrapped around his shoulders.

Personality
Aizen is a 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, and is willing to use almost everyone around him as pawns to achieve his goals. He is willing to stop at nothing to further his ambitions, including manipulating or killing anyone if he deems it to be necessary. He frequently toys with his underlings for amusement.

During his time as a captain, Aizen liked tofu, but he disliked boiled eggs. In his free time, he often read, and he gave a special lecture of calligraphy at the Shin'ō Academy because 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 through acquired respect or fear. Ulquiorra Cifer revealed to Orihime Inoue that they are all there to further Aizen's ambitions. Aizen keeps more rowdy individuals like Grimmjow Jaegerjaquez in line through intimidation and mind games. The Arrancar Aisslinger Wernarr claims the Arrancar follow him because he has no fear, something which beings born from fear and despair find inspiring.

Gin Ichimaru has some sense of Aizen's emotions and feelings, correctly pointing out Aizen was enjoying the invasion by Ichigo and his friends and their successes within Las Noches, which Aizen himself confirmed, and noting Aizen was surprised by the arrival of Momo during the battle of Fake Karakura Town. In contrast, Kaname Tōsen has shown no such understanding, and has fallen victim to one of Aizen's more minor mind games when Aizen subtly 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 Soul Society. As he and his fellow traitor captains were departing from the Soul Society, he told 13th Division Captain Jūshirō Ukitake "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".

According to Kisuke Urahara, since mastering the Hōgyoku, Aizen has become less cautious in battle, for Aizen would not have allowed Urahara to use level 90 Kidō before he subdued the Hōgyoku. Aizen admits his new powers allow him to let his guard down. Due to this newfound power, Aizen has developed an 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 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 which he does not understand; for example, when witnessing Ichigo Kurosaki use Saigo no Getsuga Tenshō, Aizen becomes furious because he is unable to comprehend how a Human has surpassed him.

By the time he is released from Muken, he has reverted to his calm, casual personality, brushing aside Shunsui Kyōraku's praise regarding his current abilities, and somewhat undergoes a change of heart, even being willing to fight against Yhwach and assist Ichigo before returning to Muken. He disagrees with Yhwach's philosophy about combining all three planes of existence to eliminate the fear of death and believes that people would never have the courage to move forward against such a threat in Yhwach's world.

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

Later, Aizen sends Ulquiorra Cifer and Yammy Llargo to find Ichigo and report on his progress. They almost kill Tatsuki Arisawa, Yasutora Sado, and Orihime Inoue, and Yammy manages to kill a large amount 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 uses Solita Vista to show what he has seen to the others and Aizen. After Grimmjow and Shawlong Koufang question Ulquiorra and Yammy on why they just did not kill them as ordered, Aizen states he is impressed with Ulquiorra's work. Later, Grimmjow and his Fracción (Shawlong, Edrad Liones, Nakeem Grindina, Yylfordt Granz, and Di Roy Rinker) invade Karakura Town without orders, prompting Kaname Tōsen to travel there, bring back Grimmjow (his Fracción were killed during their unauthorized mission), and punish Grimmjow himself when Aizen refuses to take action.

Later, after examining Orihime's powers, Aizen decides to initiate another invasion on Karakura Town, letting Ulquiorra pick the members of the invasion force, though Aizen personally sends Grimmjow as well. Ulquiorra, Grimmjow, Yammy, Luppi Antenor, 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 and reveals to the Arrancar present how Orihime's powers are rejection, meaning she can "reject" anything which has happened.

Hueco Mundo arc
Calling the Espada to a meeting, Aizen invites them to have some tea. As they are drinking their tea, Aizen reveals to them the presence of Ichigo, Uryū, and Sado. When the Espada begin to dismiss the group as not dangerous, Aizen warns them to not underestimate the trio and reveals their exploits in Soul Society. When Aizen identifies Orihime as the missing member of their group and states they have come to rescue her, Grimmjow begins to leave and states he is going to go eradicate the threat in Aizen's name. Stopping him, Aizen resorts to intimidating Grimmjow with his Reiatsu when the latter hesitates to back down. As Grimmjow is brought to his knees by Aizen's immense Reiatsu, Aizen tells the other Espada to return to their palaces and wait patiently. Telling them not to be overconfident, Aizen says they do not to be afraid because no one can defeat them as long as they are with him.

At one 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. Asking Orihime to interpret him showing her the Hōgyoku as a sign of his trust in her, Aizen asks Orihime to use Sōten Kisshun to undo some minor damage which has occurred to the Hōgyoku from being repeatedly reawakened.

Following the arrival of Ichigo and company at Las Noches, Aizen is informed of Dordoni Alessandro Del Socaccio's death by a messenger. Unsurprised by Dordoni's demise, Aizen expresses surprise at Ichigo struggling against him. Cornering the messenger by catching him in a lie of omission, Aizen demands to know who sent the Exequias after Dordoni. When the messenger does not answer, Szayelaporro Granz intervenes and reveals he is the one who did so before begging Aizen's forgiveness, which Aizen grants him. As Szayelaporro turns to leave, Aizen tells him to make his reports more thorough next time, shocking Szayelaporro, before asking him if the Reiatsu record he obtained from Dordoni will aid in his research. Confirming this, Szayelaporro leaves. Following his departure, Gin, who had been present in with Aizen the entire time, asks Aizen if he is enjoying himself even though his subordinates are losing, prompting Aizen to confess the emotion he is feeling at the moment is akin to enjoyment.

After Aaroniero Arruruerie, Szayelaporro, Zommari Rureaux, Grimmjow, and Nnoitra Gilga are defeated by Ichigo, his friends, and the invading Shinigami captains, Aizen has Coyote Starrk bring Orihime to him. Telling Orihime to smile and wait where she is while they go and destroy Karakura Town, Aizen has Tōsen use '''Bakudō #77. Tenteikūra'''. Using this, Aizen reveals his true motivation behind the capture of Orihime to Ichigo and the others: by kidnapping Orihime, he inspired Ichigo and his friends to attempt a rescue, thereby depriving Soul Society of a valuable military asset, and when four captains assisted in her rescue, adding to the three which had already defected, Soul Society was left at half its regular strength, so he and his forces are now ready to attack. Leaving with Gin, Tōsen, Tier Harribel, Baraggan Louisenbairn, Starrk, and their Fracción to invade Karakura Town, Aizen leaves Las Noches in the hands of Ulquiorra.

Inventions

 * Aizen has stated he arrived at the conclusion of the Hōgyoku before Kisuke Urahara, though 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 was not satisfied. According to the experimental data, Urahara's Hōgyoku was also incomplete, so Aizen decided to steal this 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 amounts of Reiryoku and not souls with low amounts of Reiryoku. Those infected experience great sickness and fatigue until they vomit up a white liquid, which forms the beginnings of their Hollow mask before proceeding to transform their bodies and warp their minds. Other than this, all which is known is 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 traps a subject in an alternate dimension from which there is no escape; however, this assumes it is being used as intended; it was meant to punish weaker Arrancar for disobeying the Espada commanding them. 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 Shinigami 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, all of these ended in failures. After his defection, he began using the Hōgyoku to create Arrancar who were far more powerful than naturally occurring Arrancar. Aizen gave 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 Reiatsu. Aizen used this cloak to sneak up and attack Isshin Shiba. Aizen states it allows the wearer to blend in with the air around them by incorporating Kidō into the cloak, almost completely concealing them from sight.

Powers & Abilities
Genius Intellect: Arguably, the most fearsome trait of 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 and its method of creation. He has created several Hollows and Arrancar while avoiding any suspicion from the majority of Soul Society. For over 110 years, he had been engaging in experiments involving unique and highly dangerous manipulations of Reiryoku and Reishi, including experiments involving the Hollowfication of Shinigami, something which had never been done before. He has an innate knowledge of the Hōgyoku, rivaling that of its creator, Kisuke Urahara, even knowing how to destroy it. He figured out the true nature of Shinji Hirako's Shikai, allowing him to counter its effect. He effectively deduces the true nature of the Hōgyoku via trial and error of the situations which revolve around it.


 * Master Manipulator: Aizen has proven himself very crafty and a cunning man since his public betrayal of Soul Society. He can deceive and manipulate others around him in different ways for a variety of purposes. For years, he convinced everyone around him 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 understand a person's pattern of thinking and better manipulate them. He can formulate well thought out plans several steps ahead of others, some of which have a long term in mind. 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 at plans within plans, such as kidnapping Orihime, allowing him to use her abilities to extend the shelf life of the Hōgyoku and lure many of his enemies into Hueco Mundo to trap them, making it easier for him to accomplish the goal invading the Royal Palace.


 * Master Strategist & Tactician: Aizen has proven himself to be a masterful and flexible tactician, 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 Captain-Commander Genryūsai Shigekuni Yamamoto, a Shinigami whose abilities surpass his own. Despite viewing his power as worlds beyond others, Aizen is highly cautious in battle, placing special protections on himself so as to leave no blind spots.

Kidō Master: Aizen has immense proficiency in using Kidō spells. He is well-versed in a variety of Kidō types and skilled enough to use even high-level Kidō without the use of their incantation, such as Hadō #90 to disable 7th Division Captain Sajin Komamura, albeit only at a third of its power. Even during his time as a lieutenant, he could block high-level Hadō spells such as Hadō #88 from the likes of Tessai Tsukabishi, captain of the Kidō Corps and the most proficient Kidō master in Soul Society at the time, with Bakudō #81. He can also produce powerful protection spells while in battle. After his imprisonment in Muken, Aizen is able to cast the strongest Kidō at full power effortlessly, including using Hadō #90 while he was still restrained to a Reiatsu-suppressing chair, and Hadō #99, the highest-level offensive spell of all.

Shunpo Master: Aizen is so fast, opponents commonly cannot discern even being attacked by him until after it has taken place. Aizen can easily outmaneuver Ichigo's Bankai and Hollow mask-enhanced speed, to the point where he could casually lay a hand on Ichigo's chest and still dodge a point-blank attack. Aizen can dodge simultaneous attacks at close-range and evade Bankai-level techniques, and even when being attacked from behind.

Master Swordsman: Aizen is a highly skilled swordsman, with his skill supplemented by his immense strength. He can perform tremendously powerful and precise strikes and cut through very sturdy targets, such as Renji's Shikai and Komamura's Bankai. He cut down four captains (two of which used their Bankai) and four Visored (with three being former captains of Gotei 13) with ease, and easily overpowered a Hollow mask-enhanced Ichigo Kurosaki.

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

Immeasurable Spiritual Power: Even by captain standards, Aizen possesses a tremendous amount of Reiryoku. When Aizen noted that the Hōgyoku in its half-awakened state can be fully activated when temporarily fusing with someone with at least twice as much spiritual power as an average captain-level Shinigami, he calmly proved able to do so himself. He claims he is more powerful than all of the Espada. Even after spending a year and a half sealed away in Muken and losing most of the powers granted to him by the Hōgyoku, Aizen's Reiatsu increased to the point where restraining him to a Reiatsu-suppressing chair after his release was necessary to keep it in check, and Urahara claims he has become even stronger than when he fought Ichigo. His Reiatsu is violet. His immense Reiatsu is the reason why Aizen was chosen as one of the 5 Special War Powers by the Wandenreich.


 * Masterful Reiatsu Control: 2nd Division Lieutenant Marechiyo Ōmaeda stated Aizen's mere presence is monstrously overwhelming. The force of Aizen's Reiatsu is great enough to, without any effort, bring Grimmjow Jaegerjaquez, the 6th Espada, to his knees. He has stated it takes a lot for him not to "crush an ant" (referring to Renji, the Sixth Division lieutenant) in his path. Aizen's Reiatsu is powerful enough to nullify abilities such as Suì-Fēng's Nigeki Kessatsu, and allow him to remain conscious under the effects of NaNaNa Najahkoop's The Underbelly. After being released from Muken, Aizen displays the ability to use his Reiatsu as a shield that can vaporize living beings that come too close to him, similar to his previous forms when fused with the Hōgyoku. He can focus his Reiatsu to break through dense barriers that are permeated with Reishi.

Immense Strength: Aizen is strong enough to stop the blade of 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 sword strike. He can stop the Shikai of both Renji Abarai and Sajin Komamura with just one hand and destroy the former's with a single swing, proving his strength is more than enough to combat a captain-level opponent. Aizen further displays his strength by cutting through the sword and wrist of Komamura's Bankai. Immediately after Shunsui Kyōraku used one key to remove the seal on Aizen's mouth in Muken, Aizen was able to move freely from his bindings without any further intervention from Shunsui.

Immortality: Due to his interaction and subsequent fusion with the Hōgyoku, he has gained some degree of immortality, allowing him to regenerate from the damage caused by Ichigo's Mugetsu (albeit at the cost of his new Hōgyoku powers) and live past his 20,000 year sentence in Muken. He took no damage from using Hadō #90 on himself in an attempt to free himself from the Reiatsu-suppressing chair he was restrained to, despite the technique having destroyed all of Yhwach's remaining eyeball creatures and most of his surroundings. Later, he remained unfazed after being dismembered and impaled by a Soul King-empowered Yhwach, and survived being engulfed by his immense and chaotic Reiatsu.

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.


 * Shikai Special Ability: The special ability of Kyōka Suigetsu is . It controls the five senses to the point where it can make the target misinterpret another person's form, shape, mass, feel, and smell to be an enemy's. The initiation condition for the hypnosis is for the enemy to see Kyōka Suigetsu at the exact moment it is released. After seeing it just once, this person will completely succumb to the hypnosis every time it is released, regardless of how long ago they saw it, as the Visored remain affected even after 110 years. When Aizen turns off the hypnosis by force of will, the image shown melts away or shatters. The complete hypnosis of Kyōka Suigetsu is absolutely flawless; even if the target is aware of being under the hypnosis, they cannot resist its influence. The hypnotic abilities of Kyōka Suigetsu make it a highly useful tool in combat, for Aizen can 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 is too late to react. After the Hōgyoku disintegrates his Zanpakutō, Aizen is still able to use its illusionary powers, even against Yhwach's The Almighty; however, unlike previous usage of the "Complete Hypnosis" granted by his Shikai, Aizen implies that he isn't aware of what Yhwach is perceiving at the time, and would have no control over Kyōka Suigetsu's influence on Ichigo had he been exposed to its release. Additionally, the hypnosis only lasted until Yhwach revived himself.


 * Bankai: Not Revealed.

Former Powers & Abilities
Upon fusing with the Hōgyoku, Aizen goes through a series of transformations. His appearance returns to normal after getting hit by Ichigo Kurosaki's Mugetsu. Kisuke Urahara suspects that the Hōgyoku had rejected Aizen, though Ichigo believes the Hōgyoku had reacted to Aizen's hidden desire to be like everyone else after feeling Aizen's loneliness in their battle. Despite losing access to these forms, Aizen retains his immortality and tremendous Reiryoku, and eventually surpasses the forms by the Quincy Blood War.

Zanpakutō
Sight Requirement: Because Kyōka Suigetsu's release must be seen for victims to succumb to the hypnosis, its ability does not work on the blind or those who have not seen its release.

Near Flawless Illusions: 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. 4th Division Captain Retsu Unohana detected something was amiss with Aizen's fake corpse, even though she did not realize what it was until seeing Aizen alive.

Reiatsu Presence: The Reiatsu of Kyōka Suigetsu gives it away to those who are unaffected by the hypnosis or those who are keen enough to sense its actual presence while under the hypnosis.

Touch Negation: The sole way to escape the ability of Kyōka Suigetsu is to touch the blade itself before complete hypnosis is activated.

Appearances in Other Media

 * Aizen is an unlockable character in many of the Bleach video games. Because he is the central antagonist, he is often the final boss, such as in Soul Carnival.
 * Aizen makes use of his Zanpakutō's abilities throughout most of the games, but Hadō #90. Kurohitsugi is one of Aizen's best attacks. In Shattered Blade, Versus Crusade, The 3rd Phantom, The Blade of Fate and Dark Souls, Aizen can use other Kidō spells like Hadō #33. Sōkatsui and Bakudō #61. Rikujōkōrō.
 * In Soul Resurrección, Aizen appears in his Second, Third, and Final Fusions, but is only playable in his Third Fusion. In these forms, he can use Kidō and is the game's final boss. Additionally, he is the only character who can move while blocking, though he is also the only character who walks and does not run.
 * In Soul Resurrección, Aizen's Ultrafragor ability, upon completion, creates a massive explosion which does heavy damage.
 * Aizen is playable in all his forms in Bleach: Brave Souls, including the Muken version, which was released as part of the commemoration for the Thousand-Year Blood War arc gacha tie-in. In this form, Aizen is a ranged character with the "Hollow Killer" ability who can inflict Weaken with every attack, and he is unique among other characters as the first to display a 3-way third strong attack; if tapped as a normal strong attack, Aizen will unleash his weaker, incantation-less Hadō #90. Kurohitsugi in a weakened state, but if the player holds down the strong attack, the Kurohitsugi will charge to a stronger version, and at the second phase of the charged move, Aizen will start the full incantation of the Kidō, resulting in a massive blast that covers the entire screen and dealing massive damage once the third phase is reached. Muken Aizen's special attack is Hadō #99. Goryūtenmetsu, where he summons five energy dragons that devour everything in their path, inflicting immense damage and Weaken.
 * Aizen is also playable in his Quincy Blood War form in the action-adventure crossover video game Jump Force.
 * Aizen does not appear and is not referenced in any of the films; however, in the second OVA, he drinks coffee at the very end with Gin Ichimaru and Kaname Tōsen.
 * Aizen has his own Bleach Beat Collection, where he sings Shinsen and Kyōka Suigetsu.
 * Aizen features in the sixth volume of Bleach "B" Station's second season, as well as the fourth season's fourth volume.
 * BuriCon - Bleach Concept Covers features Ukitake performing "Ichirin no Hana " alongside Momo Hinamori.
 * Aizen appears in the first through seventh editions of the Rock Musical Bleach, where he is played by Kengo Ohkuchi.

Censorship

 * In episode 60 of the original Japanese broadcast of the anime, the blade Aizen thrust into Momo is censored. However, this was later uncensored in the Adult Swim broadcast and Viz Media's home video releases.
 * In the same episode, Aizen's Zanpakutō wasn't coated with blood after being removed from Momo, as it was in the manga.


 * Aizen slashing Ichigo on Sōkyoku Hill is toned down in the anime. In the manga, when Aizen slashes Ichigo, the former is shown using his Zanpakutō to slash Ichigo, leaving the latter missing a large portion of his stomach. Whereas in the anime, Aizen's Zanpakutō and the missing portion of Ichigo's stomach aren't visible.
 * In the manga, after slashing Renji, Aizen removed the latter's blood from his Zanpakutō while walking towards Rukia. In the anime however, Renji's blood wasn't visible on Aizen's Zanpakutō.

Trivia

 * "The gaze into the sun." - Tite Kubo
 * Aizen's theme songs, as chosen by Tite Kubo, are "Stand Ablaze" by In Flames and "Allegro non troppo", the fourth movement of Symphony No. 5 in D Minor by the composer Dmitri Shostakovich.
 * Aizen was ranked the 13th most popular character in the second character popularity poll, 18th in the third (which also featured his glasses being ranked 47th with 134 votes), 23rd in the fourth, and 11th in the fifth.
 * Kyōka Suigetsu was ranked 18th in the first Zanpakutō poll and 7th in the second.
 * In the second best bout poll, Aizen's fight with Gin Ichimaru ranked 4th, his fight with Shinji Hirako and his later fight against the Gotei 13 and the Visored both ranked 22nd, his fight against Kisuke Urahara and Yoruichi Shihōin in addition to Isshin Kurosaki ranked 38th, his fights with Tōshirō Hitsugaya and Genryūsai Shigekuni Yamamoto both ranked 41st, his fight with Renji Abarai ranked 58th, and his fight with Zennosuke Kurumadani ranked 83rd.
 * 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.
 * The name of Aizen's Zanpakutō, Kyōka Suigetsu, hints at its illusionary properties; the moon reflected in water and a flower in a mirror are things which can be seen, but not held. It is a Chinese saying for seeing and desiring something which is a dream which cannot be easily grasped in hand, teaching people about temptations.
 * In the manga Aizen cut down Hitsugaya before the latter attacked him. In the anime however, Aizen's brief battle with Hitsugaya was extended. Hitsugaya charges at Aizen and impales him with Daigūren Hyorinmaru, only to realize he was caught in an illusion cast by Kyōka Suigetsu, before being cut down by Aizen.
 * In the anime, the three guardians Aizen has summoned to Sōkyoku hill weren't shown. Instead, Kūkaku Shiba arrived with Jidanbō Ikkanzaka and used Raikōhō to attack Aizen before he was subdued by Yoruichi and Suì-Fēng.

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