Sōsuke Aizen

Sosuke Aizen is a Soul Reaper and the former Captain of Squad 5th in the 13 Court Guard Squads. He eventually betrayed them and defected from the Soul Society with his followers, Gin Ichimaru and Kaname Tōsen. Now reigning over Hueco Mundo, he seeks to obtain ultimate power and created an army of Arrancar to conquer the Soul Society.

Personality
Aizen initially appeared to be a calm, formal, and impeccably polite man, who at first glance seems to be kind and charismatic. However, this is only a facade. Underneath his signature charming smile and sophisticated demeanor lies a callous, sadistic, manipulative, and power-hungry nature. Aizen cares little for his underlings, viewing them as expendable pawns and will do anything to get what he wants.

As the commander of the Arrancar army, he rules his underlings through acquired respect and fear. The former is due to his remarkable charisma and charm, giving promises of better lives for them, such as with Starrk, Halibel, and Ulquiorra. However, he will resort to use intimidation to keep his more rowdy soldiers (such as Nnoitra Gilga and Baraggan Luisenbarn) in line.

Whereas some villains (even members of the Espada) show some level of honor, Aizen doesn't have any and freely declares this, calling honor a weakness and stating that hatred is necessary for survival. Aizen maintains a calm visage that rarely, if ever slips, the only exception was his confrontation with Kalgara, where he became enraged at the sight of her.

Appearance
Aizen is a tall man with brown eyes and brown hair that is swept back with a strand hanging in his face. He initailly wore Arrancar style-clothing over his ''shihakushō. ''After Orihime Inoue is taken to Las Noches, he switched to wearing full clothing similar to the Arrancar, complete with a pink sash around his waist.

Biography
Aizen's exact origins are unknown, but at some point he joined the 13 Court Guard Squads and became the lieutenant of Squad 5 under Captain Shinji Hirako. During his tenure as a lieutenant, he met a young Gin Ichimaru and, intrigued by the boy's talent, took him under is wing, though Gin secretly hated him and planned to kill him for hurting his friend, Rangiku Matsumoto. He also manipulated Squad 9 5th Seat Kaname Tōsen into serving him by appealing to the latter's sense of "justice".

100 years ago, Aizen showed his true colors by performing a Hollowfication experiment on eight Soul Reapers, including Shinji, and framed Kisuke Urahara, then captain of Squad 12, and Tessai Tsukabishi for the crime. The nine were marked for death, but escaped with the help of Squad 2 Captain Yoruichi Shihōin. However, all three were declared a criminals, causing them to flee into exile. Later, Aizen replaced Shinji as captain of Squad 5, while Gin and Tosen became the captains of Squad 3 and Squad 9, respectively.

Aizen manipulated the 13 Court Guard Squads into lowering their guard by portraying himself as a benevolent, charismatic captain who was supposedly very close to his lieutenant, Momo Hinamori. He placed them all under the spell of his Shikai, Kyōka Suigetsu, allowing him to manipulate their senses, leaving them unopposed to his true plans. He also secretly began using various methods to build an army of powerful Arrancar, the strongest of which became the Espada, to destroy the Soul Society when the time was right.

His true colors were revealed when Ichigo Kurosaki and his friends invaded the Soul Society to rescue Rukia Kuchiki, who had been condemned to death through Aizen's manipulations. After orchestrating a series of confusing events, including staging his own death and framing Squad 10 Captain Tōshirō Hitsugaya for it; massacring Central 46, the Soul Society's corrupt judicial branch; and weakening several of his enemies through various battles, Aizen revealed his treachery to his former comrades.

He stole the Hogyoku - a sphere that could help him increase his power - by removing it from Rukia's body, and escaped to Hueco Mundo, specifically Las Noches, with Gin and Tōsen, declaring that he would kill the Soul King and rule the Soul Society. As a way to further symbolize his betrayal, Aizen destroyed the glasses he had always worn as a captain and swept a strand of his hair back, revealing a more menacing appearance. He bid his former comrades farewell before disappearing into the Garganta.

At an unspecified point in time, Aizen met Master Xehanort and became aware of his plans to restart the universe in his own image. Aizen simply chose to let him do as he wishes, waiting for his chance to claim the prized Keyblade Wielder.

Synopsis
WIP