Division: 5th Resigned* 
Age: unknown 
Height: 6'1"
Weight: 163 lbs
Birthday: May 29th 
Blood Type: unknown 
Occupation: Hollow Leader, Outlaw
First Seen: Volume 009, Chapter 079

Sosuke Aizen was seen as the gentle, warm-hearted guy with a comforting smile. Everyone in the Soul Society like him for his kindness and sympathy. He even was invited and came to Toshiro’s birthday party and they seem so close together. To make it short, everyone loved him. 

But later, without any warning, he was found dead. Hinamori, the vice-captain of the 5th squad was so mad she attacked Kira with rage. She was later being held prisoner and she had found out Aizen’s will. The content of the will rally shocked her,but she blindly obeys the will. When Toshiro was about to start fighting Gin, she came and point her zanpakutou towards Toushirou,saying that he was Aizen’s murderer, according to the will. Toshiro knocked her out and continue his fight with Gin. 

Later, Toshiro and her faithful vice-captain; Rangiku, when to the Central 46 Chamber and found out that all of them were dead for at least two days. They chased Kira when he appeared and Toshiro turned back after being told that Hinamori is following him. Once Hinamori arrived at Central 46 Chamber, she was led by Gin and they went in to found Aizen, who was supposed to be dead,standing at the door. Hinamori rushed to hug him in full joy, but instead, Aizen stab her mercilessly.

Toushirou came to see the dying Hinamori, and with anger, released his ban-kai to fight Aizen. But Aizen took him out with one good strike. Unohana came later, expecting Aizen to be there,but unable to stop him. Meanwhile, Tousen caught Renji and Rukia and bring them both to the Soukyoku Hill. There they met Aizen who insisted on having Rukia. But Renji,due to his stubbornness and pride, would never let Aizen get her. 

The fighting between Aizen and Renji was about to end when Ichigo came and stopped Aizen sword with his zanpakutou. Renji and Ichigo join forces to beat Aizen but both of them were defeated in no time at all, and that also includes Komamura. Aizen told Rukia the truth behind her execution and took out the Hou-Gyoku from Rukia’s body. When Aizen, Gin and Tousen were surrounded by the captains, they managed to escape by the help from Menos grandes (Gillians).