Aizen spent several years locked up in the Muken serving his sentence, darkness and silence reigned in the place, anyone gets bored easily but not in Aizen's case

Central 46 had, so to speak, a certain compassion for him, they assumed that the reason for his evil actions was because of his loneliness, so they decided to give him a little companion

With the help of Captain Kurotsuchi he managed to make a small gigai since it was no problem for him, after another long talk they sent that small gigai to the Muken

They noticed a change in Aizen's attitude, seeing him apparently more calm and peaceful, the little gigai managed to become their friend but Aizen considered him more like a son in the current time

"Now what toy did you steal?" said Aizen in a mocking but loving tone