Gin Ichimaru vs. Sōsuke Aizen

Gin Ichimaru vs. Sōsuke Aizen is a battle that takes place after Aizen fended off the attacks of Isshin Kurosaki, Kisuke Urahara & Yoruichi Shihōin and arrives with Gin at the real Karakura Town in Soul Society to create the Ōken. It is Gin Ichimaru's betrayal of Aizen and the culmination of his preparation efforts over 100 years in an attempt to eliminate Aizen.

Prologue
In the fake Karakura Town, when Ichigo turns to look at Aizen's fight against his Isshin Kurosaki, Kisuke Urahara and Yoruichi Shihōin, Gin appears behind Ichigo and remarks that Ichigo should not turn away when he's standing right next to him. He goes on to tell Ichigo that he is no longer a warrior, Shinigami, Hollow or even a human anymore. He asks Ichigo if he thinks that he can beat Aizen when his father, Urahara and Yoruichi cannot. Seeing how weak Ichigo's resolve is, he again offers to allow Ichigo to run, saying that he has lost interest in him and that Aizen will be disappointed to see him as he is. Gin finishes by saying that Ichigo 'knows' about Aizen's power. He then tells him that is all the warning he is going to give Ichigo and that he is not going to run, he will finish him off. As Gin draws his Zanpakutō, he is stopped by Aizen. Ichigo sees that Aizen has completely defeated his opponents, all three of them lying on the ground. Aizen then asks what Gin was going to do to Ichigo, he simply replies that he was testing Ichigo's strength. Aizen instructs Gin to open a Senkaimon so that they can attack the real Karakura Town in Soul Society, remarking that there is no need to destroy the Tenkai Kecchu since it will be more convenient to create the Ōken in Soul Society if they are attacking the Royal Palace. Ichigo tells him to wait, but falls silent as Aizen's body begins to shed his sleek new form as his "incubation" is complete. Gin remarks that his incubation period has ended and Aizen agrees, finding that it fortuitous that the Chrysalis period has ended as he will be able to watch the demise of Soul Society with his own eyes. Gin opens the Senkaimon and before leaving, Aizen tells Ichigo that he will leave him in the fake Karakura Town and come back for him after everything else is done. Aizen then enters the Senkaimon with Gin. . As they travel through the Dangai Precipice World, Gin comments on the nostalgic feel of the place. Aizen agrees before they are confronted with the. Gin urges Aizen to get going but Aizen holds his ground, prompting Gin to comment that as the Kōtotsu is a being of reason and not Reiatsu, as such, nothing can be done to it with Reiatsu. However, Aizen continues to hold his ground and then destroys the Kōtotsu as it gets close. Aizen then asks Gin what he is afraid of, saying that reason is for those who cannot live without clinging to it. Aizen then invites Gin to come with him to reason's horizon. Once they arrive in Soul Society, Aizen notes that they are some distance away from where Karakura Town is. Gin asks Aizen not to make it sound as if it was his fault, blaming it squarely on Aizen's destroying the Kōtotsu. Aizen concedes that, that might be the case and apologies before starting to walk towards Karakura Town.

When Gin and Aizen arrive on the outskirts of Karakura Town, Aizen notes that it is likely to be the last time they see both Karakura Town and Soul Society. While in the real Karakura Town, Gin spots Tatsuki Arisawa helping to move her friends, whom Aizen identifies as Ichigo's ally. As they approach Ichigo's friends, Keigo runs away from them. Aizen tells Gin that there is no need to follow him and that they will start with Tatsuki. However, before they can do anything, they are interrupted by Don Kanonji who hits Aizen in the face with his Kan'onball attack and then strikes his trademark pose. Gin, along with Tatsuki, are dumbfounded by Don's antics. As Kanonji proceeds to charge Aizen, he is stopped by Rangiku - who tells both Aizen and Gin that she made it in time.

After Rangiku forces Kanonji to run away, Gin asks Aizen leave him to talk with Rangiku elsewhere. Aizen tells him to take his time and assures Gin that he won't be inconveniencing him. Gin grabs Rangiku and flies up with her with Aizen remarking to himself that Gin is an interesting child as always. As Gin takes Rangiku away, Rangiku tells him to let her go and eventually breaks free to land on the roof some distance away from him. He then asks her what she is doing there when she can barely stand and she explained that she opened a Senkaimon as soon as his Reiatsu disappeared. Gin tells her that he didn't ask her how she got there but what she was doing there. Rangiku answers that it is because of him and that now she can ask him why he's following Aizen and why he betrayed Izuru Kira who had so much faith in him. Gin in-turn asks if that's seriously what she is asking him and demands to know if it was really Kira's faith in him that was betrayed. He then approaches her, saying he doesn't know why she came and upon getting close to her draws his Zanpakutō on her, telling her that she's in the way.

Battle
He then casually walks by Aizen as the Ichigo's friends run off, prompting Aizen to state that he is tired of playing cat and mouse. Gin then asks what he intends to do with them, to which Aizen states that after killing them he will hang their corpses in a visible location outside of town and then they shall begin creating the Royal Key. Gin tells him it sounds good as he will be the one to kill them all, he then places his hand on Aizen's Zanpakutō blade. Gin then throws up his sleeve and releases Kamishini no Yari from under his arm impaling a surprised Aizen through the chest. Gin looks back at Aizen and states the sole way to escape Kyōka Suigetsu's ability is to be touching the blade itself before "Complete Hypnosis" is activated. He ponders about how getting that information out of Aizen took many decades. He then states that despite not a single being in the Gotei 13 knowing that fact, they all intended to kill Aizen nonetheless. As Gin retracts his Zanpakutō he admits that watching them try kill him gave him anxiety, since the only one who can kill Aizen is him. As blood flows out his chest Aizen grabs his wound and tells Gin that he knew all along and he brought him with him to see how he would go about trying to end his life, but he mentions how unfortunate if he thought that attack would do it. Gin interrupts stating that he never imagined that it would. He then has Aizen take note of a nick in the blade of his Zanpakutō. He then points to Aizen and states he put that little missing piece inside him. Aizen is confused as Gin explains he told him about his Bankai ability a long while back, he then mentions that he lied. Gin admits it doesn't extend as long as he said and doesn't move as fast, either. It simply turns to dust for one moment while extending and contracting. While in the interior of the blades a deadly poison capable of breaking down cells is secreted. Aizen is surprised at the revelation as Gin senses he now understands that during the time between striking his heart and pulling his sword back, he left a tiny sliver of that dust right in his heart. Aizen attempts to say something but Gin simply tells him if he intends to speak he should do so soon, but then again no matter how quickly he tries to talk he is going to die either way. Gin then places his hand up to Aizen's chest and activates his technique Kill, Kamishini no Yari. Aizen curses him as Gin simply smiles and tells Aizen that a hole will open in his chest and he's gonna die, he then mentions that's what he has always wanted. Gin then watches as Aizen chest begins to dissolve from the inside out leaving a gaping hole with the Hōgyoku floating the middle.

Gin moves to take the Hōgyoku but Aizen grabs ahold of his wrist and throws him, but Gin still gets away. Gin goes around the side of a nearby building and looks at the Hōgyoku in the hand of in his now injured arm. He then senses an eruption of a large amount of reiatsu as Aizen emerges with a new form. Aizen states that this is his victory and that, whether the Hōgyoku Gin stole was within him or not, it is already his. The Hōgyoku in Gin's hand begins to glow prompting Gin to wonder what is happening. As Aizen draws near with the the center of his chest radiating light as Gin turns to face him. Aizen slashes him vertically across the chest. The Hōgyoku disintegrates in Gin's hand and reassembles itself in the cross-like structure at the center of Aizen's chest. Gin reaches for it but Aizen grabs him by the wrist, rips off his right arm, and impales Gin through the chest with his blade. Aizen then states that fear is necessary for evolution, the fear that one could be annihilated at any moment. He then thanks Gin for his efforts as he now has risen to an existence that surpasses both Shinigami and Hollow. Aizen throws Gin into a nearby building.

Aftermath
Rangiku arrives unharmed and screams his name, she holds him in her arms and cries. As Gin slowly dies, he affirms to himself that he failed, as in the end, he couldn't get back what was taken from her and that he is glad he said he was sorry. Upon Ichigo's arrival Gin notices the strength in his eyes after only seeing the despair in them previously, he then takes solace in the fact that he can die and entrust the task of killing Aizen to him.