A few years after the Thousand-Year-Blood-War. Kurosaki Ichigo, Inoue Orihime, Kuchiki Rukia, Renji Abarai and the other Gotei 13 members (+Arrancar) along with Aizen were on a patrol in the World of the Living. Aizen was freed from Muken to help with the Shinigami once in a while, and although he
