Invasion of Soul Society

The Invasion of Soul Society was a major conflict detailing Sōsuke Aizen's and Gin Ichimaru's attack on the Real Karakura Town located in Soul Society, and the final battle between Ichigo Kurosaki and Sōsuke Aizen

The conflict started when Aizen and Gin arrived in Soul Society where the Real Karakura Town was located and started to chase down Ichigo's classmates, Keigo Asano and Tatsuki Arisawa

The conflict ended when Ichigo arrived after having learned the Final Getsuga Tenshō to confront Aizen in a final battle and defeat him. Aizen was then sealed by Kisuke Urahara and Ichigo lost his Shinigami powers due to the use of the Final Getsuga Tenshō.

Prelude
Having defeated their challengers in the fake Karakura Town, Sōsuke Aizen and Gin Ichimaru head through the Dangai Precipice World in order to reach the real Karakura Town in Soul Society. Soon however, they are confronted by the Kōtotsu and Gin warns Aizen to hurry up as they can do nothing to stop it. Aizen however, walks up to it and allows it to collide with him, leaving himself unharmed and the Kōtotsu destroyed. Aizen then invites Gin to carry on with him towards the Soul Society

Back in the fake Karakura town, Isshin Kurosaki hobbles towards his son and headbutts him to pull him out of his state of awe. Ichigo says that their situation is hopeless as they cannot defeat Aizen with that amount of Reiatsu. Isshin realizes that Ichigo is able to sense Aizen's Reiatsu and tells him to come with him as if he does not, all of Karakura Town will be destroyed and his friends will die. Ichigo regains his resolve and the two head open a Senkaimon.

Meanwhile, in Soul Society, Aizen notes that they did not end up at Karakura Town but rather a little ways away from it. Gin asks Aizen not to make it sound like it was his fault as it was Aizen's destroying of the Kōtotsu that made them land here. Aizen admits that it is true and the two walk towards Karakura Town.

In the Dangai, Isshin and Ichigo run towards Soul Society when Isshin stops and notes that he cannot sense the Kōtotsu. Isshin says that this gives him an opportunity to have Ichigo learn the Final Getsuga Tensho. Isshin explains that the Dangai is cut off from time and space and that time flows faster here. This means spending considerable time in here will result in little time passing outside. Isshin explains to Ichigo that he will stop the current as Ichigo enters Jinzen.

Early Stages
Keigo Asano wakes up in Karakura town and notices that everyone else is asleep. He runs into Tatsuki Arisawa who has found Chizuru Honshō and Michiru Ogawa, both of which are sleeping too. Each of them carries one of the girls and they decide to explore the area. At the same time, Aizen and Ichimaru arrive at the border of the town.

Ichigo awakes in his inner world, which is submerged in water and is met with Tensa Zangetsu, who attacks him and refuses to teach him the Final Getsuga Tenshō. He recriminates Ichigo for having fallen into despair and pulls Hollow Ichigo out of his chest. Meanwhile, in Karakura Town, Aizen finds Tatsuki and Keigo and threatens their lives. Tatsuki tells Keigo to run while she stays behind.

In Ichigo's inner world, Hollow Ichigo and Tensa Zangetsu merge as the latter explains that Ichigo's battle shall be with the two of them, as they both are the two parts of Ichigo's power. In Karakura Town, Aizen prepares to kill Tatsuki when Don Kanonji steps in to save her, but becomes another target for Aizen. They are both saved again by the arrival of Rangiku Matsumoto.

Middle Stages
Rangiku tells Don Kanonji to run. Gin asks Aizen if he can talk with Rangiku elsewhere. Aizen allows it and Gin grabs Rangiku and runs off with her. Aizen notes that Gin is an interesting child. Rangiku manages to break free of Gin. She tells Gin that she is here because of him and wants answers from him. Gin however, raises his Zanpakutō to her and tells her that she is in his way.

Gin returns to Aizen and says that he has killed Rangiku. Aizen says that he had believed that Gin held some feelings towards Rangiku but Gin says that he is a snake and does not have feelings. Gin walks by Aizen and Aizen tells Gin his plan. Gin says that it is good and places his hand on Aizen's sword. He then releases Kamishini no Yari from under his sleeve and it impales Aizen. Gin explains the only way to escape Kyōka Suigetsu's abilities. He says that he had known that he was the only one that could kill Aizen. Aizen says that he knew Gin would betray him and brought him to Soul Society to see how he would do it. Aizen mentions however, that Gin's attack would not kill him. Gin then explains the true poisonous nature of his Zanpakutō and activates it, leaving Aizen with a gaping hole in his chest.

Gin goes to grab the Hōgyoku but Aizen tries to stop him. Gin makes it out with the orb and looks at it. Suddenly, an eruption of reiatsu reveals that Aizen has entered a new form. Aizen states that the Hōgyoku is already his whether it is with him or not. He approaches Gin and slashes him across the chest. The Hōgyoku then crumbles in Gin's hand and reforms in the center of Aizen's chest. Aizen grabs Gin by the wrist and tears his arm off and stabs him in the chest. He thanks Gin for helping him evolve and throws him into a nearby building. Rangiku, unharmed, runs for Gin. She holds his dying body in her arms and cries. Gin affirms that he has failed and apoligizes to Rangiku. At this moment, Ichigo arrives with a new look and carrying Isshin on his shoulders.

End Stages
Ichigo senses that Karin and Yuzu are safe and Aizen notes that he can't feel any reiatsu coming from him. Gin notices the strength in Ichigo's eyes and decides he can leave the rest to him. Ichigo asks Aizen to fight somewhere else and pushes him to the outskirts of the town.

Ichigo and Aizen start fighting, the latter speaking of the superiority of his evolution and the power he has gained. Ichigo surprises him by stopping a blow from his zanpakutō with his bare hand, which prompts Aizen to use a full incantation Hadō #90 Kurohitsugi, but it is ineffective. Ichigo then slashes Aizen with his zanpakutō.

Aizen evolves once again and appears to take the upper hand of the battle, injuring Ichigo's left arm. Ichigo then decides to give and end to the battle, entering the Final Getsugo Tenshō. He reminisces the last of his fight with Tensa Zangetsu, in which he allowed himself to be stabbed by the spirit, and Tensa Zangetsu's admission of his wish to protect Ichigo.

Ichigo tells Aizen that the Final Getsuga Tenshō consists of him becoming The Getsuga, but that it will cost him his Shinigami powers. While Aizen ponders if Ichigo could have really surpassed him, Ichigo uses Mugetsu and the sky turns black.

Aizen survives Ichigo's attack and he tries to attack Ichigo, whose powers are starting to disappear. Aizen's zanpakutō disappears as he claims he has reached a new level of evolution, but instead, a Kidō seal is activated and Kisuke Urahara appears revealing he implanted that seal when they battled in the Fake Karakura Town. Urahara explains the Hōgyoku has rejected Aizen as its master. Aizen confronts Urahara about his ideals and the nature of the Spirit King but he is sealed within the Kidō.