The central dojo of the Infinity Castle.
Asuka and Kokushibo's battle had entered its final, life-or-death sprint.
"Caw! Caw!"
"Zenitsu Agatsuma! Upper Rank Six! Defeated!!"
Did he succeed? The crybaby.
The crow's message arrived. The thunder from Zenitsu's side had subsided, and Asuka's tightly wound nerves finally loosened slightly.
That brief moment of slack—
Kokushibo seized it.
[Moon Breathing, Fourteenth Form: Catastrophe, Tenman Crescent Moon]
The massive, grotesque blade unleashed several rainbow-like slashes descending from above. Each crescent shadow was enough to cleave through entire platforms and buildings.
Asuka blocked quickly, but the fragmented moon blades seemed to possess a will of their own. They bypassed his defense and shaved away a large chunk of flesh from his left shoulder.
"You lost focus," Kokushibo's six eyes were as cold as a god's. "Before my blade, any distraction is fatal."
"Heh, not necessarily."
A faint smile curled at the corner of Asuka's lips.
"Haven't you noticed yet?"
"…What?"
At that prompt, unease surged in Kokushibo's heart.
With prolonged contact between their blades, Nugata's greedy spiritual pressure had already begun to seep into his weapon.
The eyes on Kokushibo's grotesque blade were dimming one by one.
"Your sword… seems to be getting eaten by me."
"And honestly, if it weren't for durable demons like you Upper Ranks, I wouldn't even know who to test this ability on…"
"Tear them apart, Nugata."
"What nonsense are you spouting?"
Seeing the shift in Asuka's aura, Kokushibo felt a bad premonition.
This brat still had a trump card? Even Sun Breathing, the Crimson Blade, and the Mark weren't his limit?
What exactly is he?
These past days… even earlier, Asuka had been thinking about developing his Zanpakuto's abilities.
He couldn't grasp Nugata's limits, nor did anyone teach him.
So far, he clearly understood three abilities.
Barking. Roaring. And Tearing.
These names were nothing more than random shouts born from his emotions, yet they had become deeply bound to his blade.
In its Barking state, the Zanpakuto could unleash swarms of vicious hounds formed from spiritual pressure.
These beasts were barely under Asuka's control. They simply tore toward a designated direction, sometimes even attacking each other.
Fortunately, their damage didn't affect him. They were mainly used for probing and restraining enemies.
The Roaring state was far more extreme. It could only be used when Asuka's emotions surged, when his battle intent burned fiercely.
The blade compressed spiritual power into red-black slashes that carved deep trenches into solid mountains.
The power was immense, the destructive force overwhelming—but it was somewhat slow, giving enemies time to react.
As for Tearing… it was something Asuka had only recently grasped after integrating the five breathing styles.
And now—
It was time to test it.
"What does your body feel like right now? Pain? Stiffness? Or just numbness?"
"Utter nonsense!"
Kokushibo slashed again, but Asuka didn't meet it head-on. With nimble footwork, he evaded.
He looked at Kokushibo seriously. "If you don't tell me, how am I supposed to know if it works? How can I improve my swordsmanship?"
"Silence!!"
Kokushibo wasn't unaware—he had already realized something was wrong.
Strands of foreign power were rampaging inside his body.
It felt similar to the flames that once burned on his body and blade, yet entirely different.
They were small, but tenacious.
Again and again, Kokushibo tried to devour them with his demonic power—but they slipped away every time.
Even when he tore open his flesh and ripped off chunks of meat, these things stubbornly burrowed deeper into him, refusing to leave.
"You don't want to say it, but I can roughly sense it."
"I changed my approach. I split Nugata's spiritual pressure into small portions and let it seep into your body through every exchange."
"Once or twice, you won't notice. But by the time you do, Nugata's power has already spread throughout your entire body."
"As Shinobu would put it, this is called a virus."
Asuka dodged another furious Moon Breathing attack, explaining calmly—also organizing his own thoughts.
He pointed at Kokushibo's abdomen, which had begun to rot, and said thoughtfully, "Look, the virus is starting to work."
"Shinobu's fighting style has its value. Sometimes it's not just about overpowering your enemy—you also need to gain the upper hand in subtle ways."
"You despicable wretch! Poisoning your opponent in a swordsman's duel!"
Kokushibo roared in fury, slicing away the decaying flesh in an attempt to regenerate—but the virus had already spread.
Nugata's spiritual pressure rampaged within him, breaking down Muzan's cells from the inside out.
Despicable? Don't be ridiculous—you're a demon.
If it kills demons, then this is a blade of justice.
The starving hounds formed from spiritual pressure would never miss any chance to devour flesh. Even if beaten back or forced aside by their own kind, they would cling stubbornly until the very end.
One or two might not matter—but once they gathered in swarms and were detonated within the body, their destructive force was enough to collapse any enemy from within.
And Asuka's swordsmanship was no slouch either.
"Ripping Void!!"
The Zanpakuto slashed down through the air. Kokushibo, enduring his body's collapse, could barely defend.
His movements grew slower.
His openings grew larger.
At that moment—
He felt the approach of death.
He remembered centuries ago, when he was still human—when he was Michikatsu Tsugikuni.
"The inheritance of Breathing Styles is despairing. To this day, no one has fully mastered Sun Breathing."
"The Demon Slayer Corps has no swordsmen at our level. If we die, what then?"
"All these refined techniques… will they simply be lost?"
Michikatsu stroked his Nichirin Blade, frowning as he looked at the tall man before him—the one wearing sun-shaped earrings.
The man turned, calm and unconcerned.
"Brother, you worry too much."
"You place too much importance on us. We're just two passersby in humanity's long history."
"A child with talent far surpassing ours might be born somewhere right now. Someone will reach our level."
Yoriichi Tsugikuni gazed at the distant sky, smiling gently.
"We only need to let nature take its course and wait for the day our lives end…"
Even after centuries, Kokushibo remembered those words clearly.
Yoriichi… every time you smiled, it made me sick.
How could anyone surpass us? How could anyone master Sun Breathing?
But now—
All six of Kokushibo's eyes froze.
Asuka's blade burned like fire, moved like thunder. Every strike carried the brilliance of the sun, crashing into Kokushibo's blade and overwhelming him.
The person his brother spoke of—
Had appeared.
Slash—!!
His chest was split open. The heat of the Crimson Blade prevented regeneration, and the virus within was destroying his bones.
It reminded him of that night—
After he became a demon, when he faced his aging, dying brother—
That overwhelming sense of helplessness.
"This is a joke! I am the strongest swordsman! The strongest Upper Rank!!"
Kokushibo roared. His demonic power surged violently.
His severed flesh regenerated unnaturally, twisting and bulging. Spiked masses of flesh filled the wounds.
His severed arm transformed into grotesque, jointed appendages like an insect.
His split skull sprouted a terrifying, twisted horn.
In moments, Kokushibo's entire form changed beyond recognition.
Stronger or not was unclear—
But uglier? Without question.
Watching him cling to life in such a distorted state, Asuka sighed for the first time before an enemy.
"Michikatsu Tsugikuni… I'm coming."
At those words, Kokushibo felt a chilling cold, as if his death had already been declared.
So fast… why is he so fast?
No—
I've become slow.
Reflected in the flickering mirrors of the Infinity Castle, he saw his own hideous form.
He froze.
Neither human nor demon—just a mass of twisted flesh and jagged bones, struggling to survive under Asuka's overwhelming power.
Is this… the state I desperately sought?
Did I live for centuries… for this?
How ridiculous.
Sizzle—!!
Asuka's Crimson Blade burned with searing heat, cutting into Kokushibo's thick, twisted neck, producing the sound of meat frying in oil.
Slash—!
The blazing blade severed his head.
And shattered his final memory.
A small Yoriichi, holding a bamboo flute, smiling brightly at him.
His lips moved, but Kokushibo could no longer hear what he was saying.
"I only wanted… to become the moon that reflects the sun…"
The grotesque head—
Turned to ash.
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