Seeing Aiyan's arm turn into ashes, Shihouin Yoruichi's expression changed in shock.
This was the first time she had ever seen this man injured since meeting him.
More importantly, it was the first time she had seen him appear so powerless.
"Miss Yoruichi."
"In your eyes, is this the only man my brother can be?"
"Did you forget something? He hasn't even released his Zanpakutō yet."
Facing Yamamoto Genryūsai Shigekuni's terrifying Zanka no Tachi, Aizen's expression remained unusually calm.
His words instantly made Shihouin Yoruichi, who had been about to rush forward and help, calm down.
Indeed.
So far in the battle, Aiyan had not even used his Zanpakutō's Shikai, let alone Bankai.
He had been fighting solely with his Zanjutsu, Kido, Hakuda and Hohō techniques, and relying only on that, he had been able to force Yamamoto Genryūsai Shigekuni, even while wielding Ryūjin Jakka, into desperate straits.
"Disappear!"
Seeing Aiyan's arm reduced to ashes, Yamamoto Genryūsai Shigekuni was still unsatisfied. He stabbed again with Zanka no Tachi, aiming straight for Aiyan's heart.
With this strike, he intended to completely erase from Soul Society all traces of the most powerful genius in a thousand years.
"Zanka no Tachi: Higashi – Kyokujitsujin!"
The residual fire blade came across the sky, stabbing forward like the core of the sun itself.
Aiyan suddenly smiled, then raised his remaining left hand and, under the stunned gaze of Yamamoto Genryūsai Shigekuni, caught the charred black blade of Zanka no Tachi.
However—
He caught it barehanded.
This was a sword that carried heat of fifteen million degrees.
Yet his left hand did not instantly turn to ash like his right arm had moments ago.
Not even using:
Armament Reiatsu,
The Golden Light Spell,
Or even Susanoo—
He caught Zanka no Tachi with his bare hand and resisted Kyokujitsujin, an attack that erased everything it touched without a trace.
This sight—
Yamamoto Genryūsai Shigekuni, who had been utterly convinced of victory and was already thinking of rebuilding Seireitei and the Gotei 13, was completely stunned.
His eyes widened, his pupils dilated, and his eyeballs nearly popped from their sockets.
"Have you completely forgotten that I also have a Zanpakutō?"
Aiyan held the blade with one hand, looking at Yamamoto Genryūsai's expression of disbelief with a half-smile.
As soon as those words left his mouth, Yamamoto's expression shifted drastically.
"I don't blame you," Aiyan continued.
"The pressure I've put on you has been too great. Even using only my fists, you were already exhausted. You had no choice but to release Bankai. In such a state, how could you have had the leisure to think about my Zanpakutō?"
After speaking, Aiyan slowly closed his eyes.
Just a moment ago, the sky over Soul Society had been completely clear. Yamamoto's Bankai had evaporated every cloud, leaving only a blazing sun overhead.
But as Aiyan's eyes shut, a black spot bloomed in the center of that sun. It spread outward, consuming it entirely until the sun itself turned black—then kept spreading further, staining every corner of the Soul Society sky.
"Close your eyes · Kōfūin."
Aiyan murmured softly.
Night fell over Seireitei.
All the Shinigami present were stunned by the sight. Compared to Yamamoto Genryūsai Shigekuni's Bankai, a blade like the very core of the sun, the ability to shift day into night in an instant struck them with an even deeper terror.
"Tenchi ni shōmetsu · My lord rises and falls above and below the earth."
As night fell, Aiyan's Reiatsu steadily climbed.
The Reiatsu that had been suppressed by Yamamoto's Bankai suddenly reversed, overwhelming him on the spot.
Yes—
Even with only Shikai, Aiyan's Reiatsu was now higher than Yamamoto's, who held Zanka no Tachi.
More terrifying still, behind him, a twisted black void slowly manifested—then overlapped with his form.
"Is this… Bankai?"
For the first time in over a thousand years, Yamamoto Genryūsai Shigekuni felt an emotion he thought long lost.
Fear.
His grip on Zanka no Tachi tightened instinctively. It seemed that only this blade—the strongest Zanpakutō in Soul Society—could give him a shred of reassurance.
"No."
"This is just Shikai."
Although Aiyan's eyes were closed, everything appeared vividly in his mind beneath the darkness.
Clearer than sight.
Sharper than sensing Reiatsu.
It was God's vision, overlooking every living thing shrouded in night.
This was his Shikai, Kōfūin.
The power to command day and night themselves.
Until now, Kōfūin's two aspects, Light and Darkness, could only be used during noon and midnight respectively, unless Bankai was invoked. But now, without any need for Bankai, he could summon night instantly—anywhere, anytime.
Feeling the unprecedented power flowing within him, Aiyan smiled faintly.
His left hand, still gripping Zanka no Tachi, tightened slightly.
Then his regenerated right hand formed a blade-hand and thrust forward into Yamamoto Genryūsai Shigekuni's chest.
"Zanka no Tachi, Nishi: Zanjitsu Gokui!"
To Yamamoto, the strike looked like boundless darkness swallowing him whole.
In desperation, he activated Zanka no Tachi's strongest defensive technique—Zanka no Tachi, Nishi: Zanjitsu Gokui.
Flames of fifteen million degrees erupted, cloaking his body and blade in a blazing death shroud.
Touching him now was like thrusting into the heart of the sun itself.
Yamamoto thought Aiyan would retreat—
But instead, Aiyan advanced, his palm burning as he pierced straight through the prison garb and into Yamamoto's chest.
"Pfft!"
Blood erupted from Yamamoto's mouth as a bloody hole was driven into his chest, organs torn apart.
"You said your Bankai is the sun."
Aiyan leaned in, whispering directly into Yamamoto's ear.
"Then I am the black hole."
In that instant, Yamamoto Genryūsai could feel it clearly.
The hand inside his chest twisted and crushed everything it touched—his defensive garb, his flesh, his bones.
Even the flames of fifteen million degrees were absorbed and annihilated.
"Aiyan Sōsuke!"
"Don't underestimate the Shinigami who carry the name of the Gotei!"
Bloodied but unyielding, Yamamoto roared, his Reiatsu exploding outward.
Flames erupted violently, swelling into a massive fireball like a miniature sun.
The overwhelming heat and pressure instantly illuminated half the Seireitei, shattering the night and vaporizing everything within its range.
When the fireball finally dissipated, Yamamoto Genryūsai was left half-kneeling, using Zanka no Tachi as a crutch to support his trembling body. Blood poured from the gaping wound in his chest.
The blazing Prison Garb that had cloaked him moments ago was gone, extinguished completely.
It seemed that his massive outburst had consumed all of its power in one strike.
But Yamamoto didn't care.
His gaze was fixed firmly on the smoke-filled battlefield, eyes sharp and unyielding—
Staring at Aiyan, who had just been engulfed by the inferno, as though already looking at a corpse.
"Aiyan Sōsuke…" he muttered coldly.
"You are finished."