Sousuke Aizen is a fictional character in the Japanese manga and anime series Bleach created by Tite Kubo. He is the main antagonist of the first part of the story of Bleach. Serving as captain of the Fifth Division of Soul Reapers when he is introduced, Aizen later fakes his death and horribly betrays the Soul Society in search of immense power to overthrow and defeat the Soul King, before Ichigo Kurosaki and Kisuke Urahara defeat him in the newest iteration. His former lieutenant is Momo Hinamori.