Sōsuke Aizen

Sōsuke Aizen (藍染 惣右介) is a fictional character and major figure in the anime and manga series Bleach created by Tite Kubo. He is the former captain of the 5th Division and currently the primary antagonist of the series.

Character outline
Aizen is a soft-spoken intellectual, accented by glasses during his time as a shinigami captain. While he appears to be very kind to his subordinates, he cares very little for them in truth. According to Aizen himself, he is not bound by morals and will therefore stop at nothing to further his ambitions, including manipulating or killing anyone if he deems it necessary. According to the arrancar, Aizen is fearless, which is why they follow him.

Aizen controls his new minions either through acquired respect, as can be revealed through Ulquiorra Schiffer's conversation with Orihime Inoue where he tells her that they are all here to further Aizen's ambition, or through fear, such as when he threatened to kill Grimmjow Jeagerjaques if he attacked Kaname Tōsen. It was also stated by the arrancar Iceringer that they follow Aizen because he has no fear, which beings born from fear and despair find inspiring.

Aizen is an extremely potent combatant, well above most captain-level shinigami. While the full extent of his power remains unclear, he implies that he has reached the limit of his shinigami power in all four forms of shinigami combat: swordsmanship, hand-to-hand combat, footwork, and kidō. He goes on to state that the only way for him to advance beyond that would be to gain and master hollow powers. His mastery of the regular skills are such that he is able to stop released zanpakutō, including Ichigo Kurosaki's bankai, with one finger, and he can near-effortlessly defeat several captain-level opponents at once. A hint to his actual level of spirit power is given when he turns Wonderwice Margera into an arrancar. When preparing to activate the Orb of Distortion, he states that despite its half-awakened state, it can be fully activated when temporarily fusing with someone with twice as much spirit power as a 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, Grimmjow Jeagerjaques, to his knees.

Aizen's true objective is to overthrow the king of Soul Society. To do this, he needs the royal key (王鍵), a tri-pronged golden key that opens a portal to the dimension that the king resides in. While the location of the key is known only to General Yamamoto, Aizen knows how the original was created and how to manufacture another. In order to create the key, Aizen needs to gather 100,000 souls in Karakura Town, which has an unusually large concentration of spirit particles. Aside from killing the many souls used in its creation, creating the key will also vaporize most of Karakura Town.

During their ascent to Hueco Mundo, Aizen removes his glasses and sweeps a hand through his hair, revealing menacing eyes and a very different hairstyle. As he had previously revealed to Renji Abarai that the Aizen they all knew never existed, this would seem to be a visual representation of that claim. Before he leaves, he tells Jūshirō Ukitake that no one has been standing at the top of the world, not even God. He then says that he will be the one to stand in the heavens and end the unbearable vacancy on the world's throne. Aizen is later shown in Hueco Mundo wearing clothing similar in style to the arrancar he has been creating; he is also seated on a throne, implying that he has some level of political power.

History
Little is known of Aizen's past except that he spent much of his career in the 5th Division, eventually becoming its lieutenant. At that time, he met Kaname Tōsen and lured him to his side. Aizen became captain of the 5th Division, and saw great potential in Gin Ichimaru, who became his lieutenant and right hand man. Ichimaru and Tōsen later became captains of the 3rd and 9th Divisions, respectively, but remained loyal to Aizen. According to Aizen, even when Hinamori was his lieutenant, he thought of no one but Gin as his lieutenant.

At some point, he also saw the potential of Momo Hinamori, Izuru Kira, and Renji Abarai, and took them all into his division. While Kira and Hinamori were obedient and loyal, becoming the lieutenants of the 3rd and 5th Divisions under Ichimaru and Aizen, respectively, Renji proved to be too rebellious and was transferred to the 11th Division (and later to the 6th, where he too became a lieutenant).

Synopsis
When Rukia Kuchiki is brought back to Soul Society with the Orb of Distortion 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 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, Momo Hinamori, to believe that he was likely killed by Captain 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 amongst 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.

Aizen reveals himself by nearly killing his lieutenant, defeating Hitsugaya, and has Kaname Tōsen bring Renji Abarai and Rukia to him. Ichigo Kurosaki teams up with Renji to interfere, but Aizen displays his prowess by effortlessly disposing of them, and later finishes off 7th Division Captain Sajin Komamura with a level 90 kidō spell. Afterwards, he removes the Orb of Distortion from Rukia's body by using information researched by Kisuke Urahara, though he fails to kill her. Aizen then is brought to the Hueco Mundo by several Menos Grande along with Gin and Tōsen.

From there Aizen begins to make several arrancar, and begins sending them one by one to the material world to gain information on Ichigo and, later, to capture Orihime Inoue, who Aizen takes an interest in due to her healing abilities, which can save the powers of the deteriorating Orb of Distortion. Aizen also appears to have full faith that Orihime is loyal to him, and even allows her to see the Orb. He is aware of the intrusion of Ichigo, Chad, and Uryū into Hueco Mundo and organizes a meeting of his Espada to notify them of the threat.

Kyōka Suigetsu
Aizen's zanpakutō is Kyōka Suigetsu (鏡花水月, lit. Mirror Flower Water Moon). In its sealed form, it looks like a normal katana. Its shikai command is "shatter" (砕けろ). The phrase kyōka suigetsu suggests 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. Kyōka Suigetsu's shikai has the ability to place anyone who sees it under a state of "absolute hypnosis" (完全催眠), after which Aizen can make them see whatever he wants. The hypnosis is unbreakable, even if the target is aware that they are hypnotized. The only way to avoid the effect is to not see Kyōka Suigetsu at the moment of its shikai release, making the blind Kaname Tōsen immune to its effects. The effect seems to be permanent, or at the very least long-lasting, as Aizen uses it on nearly all of the lieutenants and captains in the Gotei 13 during a ceremonial release of his zanpakutō well before faking his own death. While the illusions Kyōka Suigetsu creates are quite powerful, they are not perfect; 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 hypnotic abilities make it a useful tool in combat as well, as Aizen can quickly create simple illusions to deceive opponents. By creating a decoy of himself, Aizen can hide his own movements and attack with impunity; his opponent, meanwhile, will remain focused on the illusion until it's too late to react. The most prominent example of this is his brief fight against Sajin Komamura, where an illusionary copy of Aizen is seen melting away after the real Aizen has moved close enough to use the devastating Black Coffin spell.