The moment Gin Ichimaru released Kyōka Suigetsu, he fell under its influence. The cellular toxin within Shinsō, meant to spread throughout Aizen's body, retreated from his head. However, because Gin had immediately activated his Bankai, Kamishini no Yari, the rest of Aizen's body dissolved.
For Aizen, as long as he wasn't completely annihilated in a single instant, his immense spiritual pressure and high-speed regeneration, fueled by the Hōgyoku, allowed him to recover from any injury.
To the hypnotized Gin, Aizen was dead. Having retrieved the Hōgyoku, he turned to face Rangiku Matsumoto and the others.
However, to Kyōraku and the others, Aizen was regenerating rapidly. They saw Gin turn towards them, oblivious to the regenerating figure behind him. They shouted warnings, but their words didn't reach him. They hesitated to attack. Who knew who Gin, under Kyōka Suigetsu's influence, might perceive them as?
One person, however, didn't hesitate.
Rangiku Matsumoto flashed forward, appearing before Gin, shielding him from Aizen's impending attack.
"Rangiku!" For the first time, fear flickered in Gin's eyes.
Clang!
…
Clang!
Aizen swung his Zanpakutō.
He hadn't felt this level of fear even during his fight against Yamamoto. Gin's attack had been a true threat, a brush with death. He wouldn't hold back. Even with Rangiku in his path, he was confident he could bisect them both.
But his blade stopped.
Ailin appeared before Rangiku, stretched out his hand and grasped Aizen's Zanpakutō, halting its descent.
BOOM!
Though the blade stopped, the force of the attack rippled outwards, shattering the surrounding buildings.
"Captain Ailin?"
The Shinigami, having dispersed the dust cloud, saw Ailin holding Aizen's Zanpakutō and Rangiku and Gin unharmed behind him.
"Captain Aizen, do me a favor, and let's end this here. How about it?" Ailin said, addressing the now winged, three-eyed Aizen
Aizen, in this evolved form, now truly rivaled Yamamoto's Bankai. Had he been this powerful earlier, Kyōraku and the others wouldn't have dismissed his victory as merely a consequence of Yamamoto's age.
Aizen stared at Ailin and is pupils constricted.
How is that possible?
He had evolved three times, yet he still couldn't perceive Ailin's movements. And that casual grip on his Zanpakutō… He had attacked with full force, fueled by rage, yet Ailin had stopped him effortlessly.
A Shinigami's battle was a battle of spiritual pressure. A Zanpakutō was the condensed form of that pressure. If one combatant's passive spiritual pressure exceeded the other's focused, amplified pressure, then the weaker combatant's attacks would be ineffective.
This was the case now. Ailin's passive spiritual pressure surpassed Aizen's focused power. Aizen's attack, despite his full strength, couldn't even pierce Ailin's skin. Aizen's Zanpakutō, gripped by Ailin, was now immobile.
This was the fundamental nature of Shinigami and Hollow combat. Shinigami focused their spiritual pressure into their Zanpakutō to kill Hollows. Hollows, in turn, condensed their spiritual pressure into their Hierro, their hardened skin, to defend against Zanpakutō. A clash between Zanpakutō and Hierro was a clash of spiritual pressures. If the Shinigami's spiritual pressure was greater, the Zanpakutō pierced the Hierro. If the Hollow's spiritual pressure was greater, the Hierro repelled the Zanpakutō.
Aizen's attacks couldn't harm Ailin.
"Very well. For your sake, Captain Ailin, I will spare Gin."
Knowing he couldn't defeat Ailin in his current state, Aizen wouldn't force a confrontation. He needed to evolve further.
"However, Captain Ailin, I trust you won't object to my retrieving what Gin stole from me."
He looked past Ailin at the Hōgyoku in Gin's hand. He needed the Hōgyoku to reach his full potential. Once he fully merged with it, even Ailin wouldn't be a threat. He had absolute faith in the Hōgyoku's power.
"Fine. Here." Before Ailin could respond, Gin tossed the Hōgyoku back to Aizen. Compared to nearly losing Rangiku, the Hōgyoku was insignificant.
"I'm sorry, Rangiku. I wanted to return what he stole, but…"
"You idiot, Gin!" Rangiku threw her arms around Gin, burying his head in her embrace. "You are the most precious treasure to me. As long as you're by my side, I don't need anything else."
"I'm sorry, Rangiku. I've put you through so much."
Ailin sighed at their tearful reunion. "Captain Aizen, I need to… extract something from that Hōgyoku. I trust you won't mind."
He extended his hand and his spiritual pressure flowed into the gem. A wisp of white light emerged, drawn into Ailin's palm.
"Alright. Carry on, Captain Aizen, Captain Kyōraku. I have some… business to attend to."
With a flash, he vanished, taking Gin and Rangiku with him, leaving Aizen and the Shinigami staring after him in bewilderment.
…
With a few Shunpo, Ailin arrived at one of the Sekkiseki with Gin and Rangiku in tow. Though he had never witnessed the Kidō Corps in action, the resilience of this barrier, even under the assault of Yamamoto's Bankai, impressed him. The barrier surrounding the replica Karakura Town had held, preventing the battle from spilling over into the real world.
"Teacher, you saved me again."
Gin released Rangiku, Two people mattered most to Gin in this world: Rangiku Matsumoto, the woman he loved and had vowed to protect, and Ailin.
When Rangiku had been attacked by Aizen, Gin, powerless to defend her, had watched helplessly from the shadows. Ailin had intervened, killing the Shinigami accompanying Aizen, driving Aizen back, and using a piece of Gin's soul to heal Rangiku's shattered spirit.
"Indeed, Gin. Of all my disciples, you've caused me the most trouble."
Ailin rolled his eyes. He remembered a young Gin, fresh out of the academy, encountering Aizen. If not for Ailin's intervention, Gin would have followed Aizen then and there. Even after that, Gin hadn't stayed by Ailin's side for long. Believing he had learned enough, he had left the Eleventh Division, tailed Aizen, killed the Fifth Division's Third Seat, and declared himself a more valuable asset.
Of Ailin's disciples, Byakuya Kuchiki, Rukia Kuchiki, and Toshiro Hitsugaya hadn't faced any immediate danger. Their trials lay in the future. And having received Ailin's guidance, he expected them to overcome those challenges. Only Gin had faced a direct threat from Aizen.
Even Aizen, after evolving three times, had nearly been killed by Gin. If Gin hadn't released Kyōka Suigetsu at the last moment, falling prey to its hypnosis and believing his toxin had spread throughout Aizen's body, Aizen would be dead.
Gin had grown stronger.
"Here. This is what you wanted." Ailin shook his head and offered the wisp of white light in his palm to Gin.
Gin stared at the light, the culmination of his years of scheming, his descent into darkness. He had become a viper, lurking in the shadows, all for this. And yet, he hadn't retrieved it himself. Ailin had extracted it from the Hōgyoku, the fragment of Rangiku's soul stolen by Aizen.
He didn't refuse. He knew he had only had one chance to kill Aizen. Having failed, Aizen wouldn't give him another opportunity. Retrieving Rangiku's soul on his own would have been impossible.
"Thank you, teacher." He accepted the light, cupping it in his hands as if it were a priceless treasure, and turned to Rangiku. "Rangiku…"
Ailin, not wanting to intrude on their reunion, vanished with a flash.
…
BOOM!
Hitsugaya's spiritual pressure erupted and he seemed to grow slightly taller. An unbearable cold enveloped him, freezing everything around him.
"Bankai – Daiguren Hyōrinmaru!"
"Shikai Hyōketsu!"
With Yamamoto's Bankai deactivated, Hitsugaya's own Bankai had returned. Having recovered, he unleashed Hyōrinmaru's full power.
Tōsen's Bankai shattered, the black barrier crumbled into icy fragments. Even the Hollowfied Tōsen was frozen solid.
Hitsugaya swayed, exhausted. He looked towards the faint spiritual pressures of his comrades, then collapsed.
During Yamamoto's Bankai, he had been completely cut off from the outside world, relying solely on his sense of touch to detect Tōsen's attacks. Enduring until Yamamoto deactivated his Bankai, and then releasing his own, had pushed him to his limit.
"Everyone…"
…
Swish!
Aizen flicked his Zanpakutō, spraying blood onto the nearby wall. Having nearly been killed by Gin, he had become more cautious. He had swiftly and decisively defeated the remaining Shinigami.
"Oh, what a failure…"
Lying on the ground among his fallen comrades, Kyōraku looked at Aizen and clenched on Katen Kyōkotsu. If he released his Bankai now, his spiritual pressure might kill his injured comrades. And even if he did, he wasn't confident he could defeat Aizen.