In Sōsuke Aizen's eyes, Kaiser had always been someone special.
Although Kaiser never claimed to be the true genius, in Sōsuke Aizen's view, in terms of talent, Kaiser was undoubtedly above himself.
He had begun paying attention to Kaiser when he was still an Academy Student at the Shin'ō Academy, even when he had just been assessed as having Second-Class Spiritual Pressure, and had always regarded him as a key observation subject, believing that he would surely hold a high position within the Gotei 13 in the future and come to his side.
In other words, the other party had the potential to affect him, even to affect his plans.
This caused Sōsuke Aizen to develop a deep interest in Kaiser, to the point that during his first inspection of the Shin'ō Academy, he personally made contact with Kaiser and even prepared a trial for him to further observe him.
Originally, his observation subjects also included Renji Abarai, Momo Hinamori, Izuru Kira, Shūhei Hisagi, and others. After all, these people were also talented individuals with the potential to become Lieutenant-level in the future, and thus had value for use. But compared to Kaiser, these people were undoubtedly far inferior.
This was confirmed during that incident.
Kaiser, who had been enrolled for only half a year, not only managed to release his Zanpakutō shortly after obtaining it, but also slew an Adjuchas-class Menos Grande with a single slash without even releasing his Zanpakutō. Later, he even defeated Kenpachi Zaraki in battle, becoming the second Shinigami in history to become a Captain without having mastered Bankai.
Later, his Zanpakutō displayed miraculous qualities, making Sōsuke Aizen realize that this man possessed abilities yet to be revealed. Thus, he began appearing frequently around Kaiser, using Kyōka Suigetsu's power to deceive everyone while silently gathering information on him.
As time passed, Sōsuke Aizen confirmed several things.
"Although he's young, he seems to have an excessive understanding of the Soul Society, and knows many things others do not."
"He should have already sensed abnormalities around him and has taken precautions against me."
"Kyōka Suigetsu most likely cannot completely hypnotize this person."
"In the future, he will be a major threat to my plan."
From this, it was clear—Sōsuke Aizen was indeed a person with great intellect, deep scheming, and immeasurable cunning.
Kaiser believed he had hidden himself very well, confident that even if someone was secretly watching, they would discover nothing. Little did he know, for Sōsuke Aizen, discovering nothing was in itself the greatest discovery.
Sōsuke Aizen had discerned from Kaiser's behavior that he had noticed the abnormality in his surroundings. He also realized that Kaiser knew many things and may have already seen through part of his own goals.
This was only natural. The fact that Kaiser had Momo Hinamori keep an eye on Rukia Kuchiki and monitor her movements—so long as Sōsuke Aizen noticed that—then with his intellect, he would naturally connect many dots.
Because of this, Sōsuke Aizen had secretly set many traps for Kaiser, some in Central 46, others within the Repentance Cell.
He believed that if Kaiser truly had discovered his objective, then to expose him, those were the places he would surely go.
But who would have thought, Kaiser had already anticipated that and didn't go to either place at all. Instead, he charged straight into the Division 5 barracks and confronted him directly.
"He knows me better than I expected. He won't fall into my trap at all."
Having realized this, Sōsuke Aizen temporarily chose to retreat and predicted that Rukia Kuchiki's Execution might not go as planned. So he made a second preparation.
Now, both sides had laid their cards on the table, but Kaiser was even more difficult to deal with than Sōsuke Aizen had imagined. His understanding of Sōsuke Aizen was also deeper. That mysterious Zanpakutō had revealed its true face, yet Sōsuke Aizen had no method for overcoming it for now.
To be able to gather the power of all Zanpakutō in the world into one, deliver slashes of terrifying might, turn offense into defense, shield its user under the protection of all Zanpakutō, and even summon the shadows of Zanpakutō to launch wide-scale attacks—that was a Zanpakutō embodying single-target offense, area attacks, defense, and power.
The king among Zanpakutō: Crown of Heavens.
This Zanpakutō was definitely more terrifying than Genryūsai Shigekuni Yamamoto's Ryūjin Jakka. In a certain sense, it was not something that Kyōka Suigetsu could be compared with.
Fortunately, Kyōka Suigetsu was an Illusion-type Zanpakutō, not a Combat-type Zanpakutō. Otherwise, Sōsuke Aizen really wouldn't be confident in defeating Kaiser in a direct confrontation.
"Looks like today ends here."
Sōsuke Aizen made a decisive decision.
"It's time to retreat."
As he said this, Gin Ichimaru had already arrived by his side. Only Kaname Tōsen remained in the front line holding off Kaiser.
Of course, with Kaname Tōsen's power, he was no obstacle to Kaiser who had already released his Zanpakutō. So Sōsuke Aizen had been using Kyōka Suigetsu to assist him, allowing him to briefly stall the five-senses-blocked, judgment-impaired Kaiser.
"Retreat already?" Gin Ichimaru stood just behind Sōsuke Aizen's side like he did when he was his Lieutenant, smiling as he said, "I thought Captain Aizen would eliminate Captain Kaiser—such a threat—before withdrawing from the Soul Society."
"At present, there's no one among the Shinigami who can break through that sword barrier and injure him." Sōsuke Aizen said without shame, "Even Ryūjin Jakka couldn't break through that layer of swords. I'm even less likely to do so."
"Oh my." Gin Ichimaru looked a little surprised. "Is Captain Aizen admitting he's inferior to Captain Commander Yamamoto?"
"It's just a difference in focus, Gin." Sōsuke Aizen smiled, "Kyōka Suigetsu is powerful, but its strength lies in its ability and deception. It doesn't have much advantage in raw attack power."
"Ryūjin Jakka, however, is recognized as the most powerful Zanpakutō in terms of attack power—at least it was, before Captain Kaiser's Crown of Heavens appeared."
"If Ryūjin Jakka can't break through that sword defense, then Kyōka Suigetsu, which lacks a clear offensive advantage, naturally can't either."
"Pretty sad, isn't it? This is the limit of a Shinigami."
Sōsuke Aizen admitted all this calmly, yet he was unwilling to compromise.
"To eliminate this threat, it would require catching him before his Zanpakutō is released—or otherwise, someone from the Royal Palace would have to act."
As for himself?
Sōsuke Aizen touched the object within his chest, the lenses behind his black-rimmed glasses flickering slightly.
"Fine. Let him witness this miracle before he disappears. That's the minimum respect due to the greatest genius in history."
"Come back, Kaname."
"Prepare for retreat."
Just as he finished speaking, Sōsuke Aizen seemed to sense something and, together with Gin Ichimaru, swiftly retreated backward.
"Boom!"
A surging blaze suddenly fell without warning, like a firestorm from the heavens, instantly igniting the ground for hundreds of meters around.
"…Where do you think you're retreating to, Sōsuke Aizen?!"
Holding Ryūjin Jakka, his entire body engulfed in flames, Genryūsai Shigekuni Yamamoto finally appeared.
He glared at Sōsuke Aizen, and pillars of fire erupted around him. The ground beneath began to show signs of melting into magma.
"Unforgivable wretch—you're going nowhere today!"
Genryūsai Shigekuni Yamamoto growled lowly.
"Even if I must offer this old, decrepit body, I will keep you here forever!"
His fury was greater than ever before, like the flames surrounding him.
But—Sōsuke Aizen smiled.
"You can no longer stop me, Captain Commander." Sōsuke Aizen calmly declared, "The battle with Captain Kaiser affected you more than I expected."
"You now have little stamina left, and even your strength has greatly diminished."
"Otherwise, you wouldn't make such an obviously bluffed attack."
With that, Sōsuke Aizen lifted his head and looked to the sky.
"The time has come. It's here."
As soon as he spoke, a strange phenomenon occurred in the sky.
Two massive hands reached out as if from another world, tearing through space itself. They pried open the sky and ripped it apart.
A gigantic Garganta appeared in the sky, from which emerged enormous figures letting out hollow cries.
"Menos Grande!"
All the still-conscious Shinigami, whether still standing or already downed, looked at the massive figures emerging from the Garganta, and their faces changed dramatically.
The next second, three golden beams of light shot out from the Garganta like celestial walls of light, landing respectively on Sōsuke Aizen, Gin Ichimaru, and Kaname Tōsen.
"Boom!"
Kaiser had just slashed toward the golden light wall, producing only a loud roar. He was unable to reach the Kaname Tōsen inside, causing the five-senses-blocked Kaiser to instantly snap back to awareness.
"This is… Negación?"
With his senses restored, Kaiser saw everything and instantly recognized the nature of the light.
Negación—beams used by Menos Grande to rescue their kin. It is a barrier that completely separates the inside from the outside world.
Once enveloped by this light, the inside and outside are like two separate realms. The person within is as if placed in another dimension, making it impossible for anyone outside to reach them.
The ground beneath Sōsuke Aizen and the other two cracked and rose into rocky platforms, carrying them skyward.
Seeing this, everyone—including Genryūsai Shigekuni Yamamoto—wore grim expressions.
They knew: now that Negación had arrived, there was no way they could stop Sōsuke Aizen's escape.
"To think you've fallen to consorting with Hollows—Sōsuke Aizen!"
Genryūsai Shigekuni Yamamoto's face was full of wrath.
Kaiser, on the other hand, stretched out his hand and pressed it against the light wall of the Negación.