The fight with Sosuke Aizen started some time ago in bleaching, during the saga of the past. It was at this point that the shinigami's plans really began to take hold, conspiring against some of the captains. Then centuries passed and everything fell into place during the False Karakura Saga.
Aizen arrives at this fictional place created by Gotei 13 to capture him. Of course, the shinigami didn't come alone and brought with them some of the strongest arrancars, leading to a unique fight against as many shinigami. However, the Vizard led by Shinji Hirako also comes to the rescue of Bleach's protagonists. Despite the victories against the Espada and their faction, Aizen's power seems too great.
The return of Ichigo Kurosaki from Hueco Mundo doesn't change things anyway Kyoka Suigetsu continues to claim casualties. Gin Ichimaru and Kaname Tosen also enter the duels, particularly the latter, who turns into a monster and loses his humanity. In the end, all the protagonists are defeated, but thanks to the help of Urahara and Isshin Kurosaki, there is still hope.
Continuing his merging with Hogyoku, Sosuke Aizen arrives at the real Karakura, where the final battle will take place. Here, Ichigo uses all the power he gained while training with his father using Zangetsu's strongest move, and Aizen is trapped, also thanks to a technique by Urahara. Conclusion of Bleach's gigantic Aizen saga.