Looking at Aiyan's Reiatsu sphere condensed on his fingertips, Unohana Yachiru already knew the answer in her heart.

Cero.

This is an exclusive ability of the Menos Grande.

Shinigami do not possess it—unless the boundary between Shinigami and Hollow is broken, the Hollow's power is mastered, and the person becomes a Visored.

However—

The scene that happened next, even if Unohana Yachiru was mentally prepared, still shocked her beyond measure.

Shu!

When the red Cero fully formed, Aiyan locked onto the sky and the bright moon, then fired the Cero—compressed to the ultimate limit—turning it into a blazing red beam. It split the night of Hueco Mundo and shot at incredible speed straight toward the moon suspended in the sky.

Boom!

As rings of red shockwaves spread out like nebulae, the bright moon—bathing the starry sky in silver light—shattered on the spot into spirit particles invisible to the naked eye.

As for the Gillian group imprisoned within the moon, they naturally turned into spirit particles as well, scattering across Hueco Mundo along with the moon's destruction.

"Just one shot of Cero can shatter the moon from such a long distance…"

Unohana Retsu's pupils contracted, and her face turned pale with shock.

As a Shinigami who had lived for more than two thousand years, there were very few things that could truly shake her.

But ever since she met Aiyan, she found her perspective being overturned far too many times this year—and every time, it was because of the man before her.

"This is Menos Grande's infant form."

"What happens when it grows up?"

"It's truly thrilling… worthy of the Reiatsu Self-Practice method—Reigen Kuzushi—that he sharpens year after year."

Aiyan raised his head, looking at the moon that had exploded and vanished from Hueco Mundo's starry sky, the corners of his mouth slightly upturned.

He knew very well that the Reiatsu training method and Reigen Kuzushi he created were not limited to this level.

Putting aside the innate abilities of both the Menos Grande infant and the Quincy infant—

The evolutionary abilities possessed by the two were terrifying enough.

Yes—

Just like the evolution of Aizen's Hōgyoku, there are multiple stages.

The Menos Grande infant nurtured in Soul Sleep and the Quincy infant in the Chain Knot are just the beginning of the Reigen Kuzushi's origin. Later, there will be adolescence, adulthood, and finally full compatibility with the soul—exchanging, reorganizing, and then evolving endlessly forever. That is the complete origin of the Reigen Kuzushi.

It was no coincidence.

When Aiyan's Reiatsu created its own energy source, nurturing Menos Grande infants and Quincy infants in Soul Sleep and Chain Knot respectively, he was tearing apart the boundaries between Shinigami and Hollow—growing and evolving step by step toward higher dimensions.

…

In the Soul Society—

Aizen had not stopped evolving.

After taking the authority of the Gotei 13 into his own hands, he—like Aiyan—left Seireitei and went to Rukongai District 80, returning to the house where he had once lived with Aiyan before entering the Shinō Academy.

Kidō barriers were set up all around—

Sealing off all perception and detection, as well as preventing any Reiatsu leakage.

After doing all this, he took out a Hōgyoku from his pocket.

Although it was not made using the Soul King's fingertips like in the original timeline, it had absorbed a large number of souls from the Four Great Noble Clans containing royal blood, as well as Soul King fragments accumulated by the Kuchiki and Tsunayashiro families over the years—plus the shattered Zanpakutō Enrakyoten, which had been passed down through the Tsunayashiro family for generations—obtaining half of the Soul King's Hakusui (Soul Sleep).

All these materials had been used to create this Hōgyoku.

At this time—

The Hōgyoku in Aizen's hand was even more perfect than the one originally fused with Urahara Kisuke's.

"It's been a month."

"With Unohana Yachiru helping him train, his Reiatsu should have reached the Shinigami limit thirty days ago."

"You haven't returned yet… are you seeking a way to break the Shinigami boundaries, or are you already attempting to shatter those limits?"

Aizen sat in a chair, gazing out the window. A deep glint of expectation flashed through his eyes behind his glasses.

"No matter which it is, you're already on the path to transcendence. I can no longer hesitate."

"Otherwise, I won't even be able to see your back."

"You agree with me, don't you… Hōgyoku?"

As he murmured, his eyes dropped to the Hōgyoku in his palm.

Tsk tsk…

In the dimly lit room, the Hōgyoku radiated a breathtaking blue-black brilliance, as if responding to him.

After a while—

Aizen seemed to understand Hōgyoku's intent. A smile tugged at his lips as he removed the Third Division captain's haori, tore away his Shihakushō, and pressed the Hōgyoku to his chest.

Tak!

The moment the Hōgyoku touched his skin, it was like a jewel set into gold and silver—perfectly merging with his body, as though it had always been a part of his chest since birth.

Instantly, a vague will surfaced within his soul, seeming to communicate with him.

Feeling this, Aizen slowly closed his eyes, immersing himself in the Hōgyoku—not to converse with it, but to tame it.

Yes—

With his pride and nature, he could not tolerate power beyond his control.

Even the Hōgyoku he had created with his own hands was no exception.

At this time—

Unlike in the original timeline, where he bore a loneliness from mind to Zanpakutō—even when fighting Ichigo Kurosaki in the Final Getsuga Tenshō, thinking that further evolution might surpass him but choosing not to—

With Aiyan's existence—

Aizen sought only to catch up, to match, or to surpass.

There was no loneliness.

Because of this, he had never abandoned the thought of evolution—in fact, it burned stronger than ever.

It was no longer merely a desire to evolve, but an urgent need.

After Aiyan—

He, too, began breaking the boundaries between Shinigami and Hollow, setting foot on his own path to transcendence.

…

First Division — Captain's Office

As the First Captain of the Gotei 13 and the absolute authority of the Soul Society—

At this moment, Yamamoto Genryūsai Shigekuni's weathered face, normally unchanging no matter the situation, revealed a rare expression of sorrow and deep internal conflict.

Especially his eyes—normally calm, sometimes filled with killing intent, sometimes with fury, sometimes with helplessness—

Now they reflected something that made even the strongest Shinigami in a thousand years feel troubled, overwhelmed, and powerless.

"Hey, Old Man Yama—

"You called Jūshirō and me here… don't tell me you're taking advantage of Captain Kirio and Lieutenant Shutara's trip to the Soul King Palace to settle old scores with us?"

"Let me warn you, Jūshirō and I already have an agreement with Captain Kirio and the others—if you dare try anything, they'll make sure you pay once they return from the Royal Guard."

At this moment, Kyōraku Shunsui's slightly roguish yet confident voice drifted in from outside the office.

"If it were just you two, you'd be easy to deal with."

"I wouldn't even have to summon you here—just send a Hell Butterfly to keep you in the Repentance Palace."

Hearing this, Yamamoto Genryūsai Shigekuni forced down the thoughts in his heart and the sorrow on his face, turning to Kyōraku Shunsui and Jūshirō Ukitake as they walked in through the door.

"Genryūsai-sensei… is this matter more serious than Urahara Kisuke's defection?"

Jūshirō Ukitake caught the faint struggle in Yamamoto's expression and felt a heavy premonition settle over him.

An unprecedented unease and anxiety surged in his chest—

Even when Urahara Kisuke single-handedly initiated the Sōkyoku Hill Execution War, or when Central 46 was destroyed, he had not felt such dread.

"…Yes."

...

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