Kokushibo?
Asuka silently drew Nugata.
According to what Hakuji had told him, among the surviving Upper Rank demons, the only one who truly required caution was Upper Rank One—Kokushibo.
"He's not an ordinary demon. He's the strongest swordsman your Demon Slayer Corps ever produced… the older brother of Yoriichi Tsugikuni."
When Hakuji first revealed this, Asuka had been somewhat surprised.
But now, judging from the aura emanating from the man before him—an aura where man and sword had become one—the statement was clearly no exaggeration.
Kokushibo slowly rose to his feet. His movements were elegant and unhurried, carrying an indescribable dignity.
He turned around.
On his resolute face were three pairs of golden eyes.
"This rhythm of breathing..." Kokushibo's six eyes simultaneously locked onto Asuka. His voice carried the decayed weight of centuries. "The aura around you reminds me of certain... unpleasant memories."
"You mean Sun Breathing, Tsugikuni Michikatsu?"
Even after being addressed so directly, Kokushibo showed little emotional reaction. He merely continued to observe Asuka calmly.
Wasn't Hakuji supposed to say this guy was narrow-minded and easily provoked? Asuka frowned slightly.
"A strange blade... and a strange power. You are not using pure breathing techniques. That chaotic force within your body—what exactly is it?"
"Want to find out?"
Asuka slowly lowered his stance.
Beneath his slightly messy black hair, his gaze turned cold as iron.
"You can try it yourself."
"Ridiculous... what arrogance from a mere junior."
Kokushibo spoke coldly as he drew the long blade known as Kyokokukamusari.
As the sword slid free, countless blood-colored eyeballs rolled wildly across its surface. An eerie moonlight flowed along the edge of the blade.
Inside the silent dojo of the Infinite Castle, the hems of both men's clothing fluttered despite the absence of wind.
It was the killing intent surging between them.
Clang!!
Neither side held back from the very beginning. Both erupted with fast and ruthless slashes.
Blades crossed. Long swords hummed. The sound of steel striking steel echoed through the night.
Kokushibo truly lived up to being a swordsman who had trained for hundreds of years. Every movement was cunning and unpredictable—far beyond what Asuka had experienced sparring with the Hashira.
The sword techniques of the Demon Slayer Corps had long been studied and mastered by him.
Even when Asuka cycled through five different sword forms, shifting unpredictably between them, Kokushibo always found a counter immediately.
"Among humans, there is only one person I have seen who could integrate breathing techniques and wield sword forms to this extent."
Kokushibo unleashed a horizontal slash that surpassed the limits of human sight, carrying countless fine crescent blades of moonlight, aimed directly at Asuka's throat.
[Moon Breathing: First Form - Dark Moon, Evening Palace]
Asuka twisted his body and spun, Nugata tearing through the air as he answered with a roaring spiritual pressure slash that sounded like a howling hound.
Boom!!
A violent storm of spiritual pressure collided with the moon-shaped blade aura, exploding at the center of the dojo. The surrounding wooden pillars instantly disintegrated into powder.
The impact was powerful enough to make the entire Infinite Castle tremble.
But Kokushibo had no intention of stopping there.
The long sword covered in eyeballs surged again.
Moon Breathing: Eternal Night Lonely Moon — Infinity
Dense waves of crescent slashes poured forth like a tidal flood.
This wide-range attack with no blind spots should have shredded any opponent instantly.
Yet Asuka's response made Kokushibo's centuries-dead eyes shrink slightly.
He moved freely through the gaps between the crescent blades, his movements completely defying common sense.
If it had to be described—
It was as if he were walking through the air.
Each time a crescent slash was about to touch him, the boy somehow found leverage from nowhere and kicked off the empty air, slipping past the attack.
"Impossible. Are you truly human?"
"More human than you, at least."
Asuka faithfully followed Hakuji's advice, constantly provoking Kokushibo with words while charging forward again.
The battle continued.
The entire dojo had already been reduced to rubble by the sword energy of the two fighters.
Wounds of varying depths began appearing across Asuka's body.
Yet astonishingly, his aura did not weaken.
Instead, it grew stronger.
"Your sword... that must be your Blood Demon Art, correct?"
Asuka brought his blade down with brutal force.
Nugata actually bit halfway into Kokushibo's sword.
A disturbing sensation traveled through his grip.
Kokushibo immediately forced Asuka back with a burst of strength, his gaze turning colder.
This feeling was not good.
Kyokokukamusari was a demon blade forged from Kokushibo's own blood and bones. Even if broken, it could regenerate instantly.
Normally, this allowed Kokushibo to unleash his sword forms freely against Demon Slayer swordsmen without worrying about damaging his blade.
But now, it had become his greatest problem.
Each time their blades clashed, Kokushibo felt a chill crawl through him.
He had already heard from Muzan that among the Demon Slayer Corps there was a black-haired swordsman capable of devouring demons.
That must refer to this sword.
Whenever Nugata cut into Kokushibo's blade, it greedily devoured the demon power within it.
Even though Kokushibo had been careful to avoid serious sword wounds, his body was still losing strength uncontrollably.
And that was not the only problem.
Asuka's breathing rhythm was becoming increasingly unsettling.
As the battle continued, the breathing flow that had initially seemed somewhat unrefined was rapidly maturing under the pressure of intense combat.
Now, the Sun Breathing that Asuka had created himself carried the overwhelming majesty of a blazing sun.
The familiar sensation grew stronger and stronger within Kokushibo.
All six of Kokushibo's eyes widened.
For the first time, his normally calm voice trembled.
"This is that man's... How can you reach that realm?"
Asuka vanished.
The only answer was a wave of blazing black-red flames rushing toward him.
No—
He hadn't vanished.
His speed had reached such an extreme that it left behind a distorted trail of fire in the air.
Kokushibo immediately raised his blade to block.
Clang!!!
It had been hundreds of years since he had felt such an oppressive slash.
The overwhelming force surged down through the sword hilt, causing cracking explosions to erupt from his bones.
Boom!!
The floor of the dojo was completely overturned. Flames mixed with spiritual pressure surged skyward, dispersing the gloom of the Infinite Castle.
Within that light, Asuka and Kokushibo passed by each other.
Kokushibo froze in place.
In his hand, Kyokokukamusari —the demonic blade covered in eyeballs—had been severed completely.
Across his chest, a deep wound ran diagonally across his torso, so deep that bone was visible.
Golden flames clung to the wound, devouring his cells and slowing his proud regenerative ability to a crawl.
"A crimson blade... no, you did not even ignite a Nichirin sword. How did you achieve this?"
Kokushibo slowly turned around, all six eyes locked onto Asuka as he voiced his incomprehension.
His tone was filled with jealousy.
But even more than that, there was a twisted excitement.
"It seems... I finally have the chance to test the full power of this form."
Just as Asuka severely wounded Kokushibo, good news was arriving from other corners of the Infinite Castle.
Within a deep corridor, the Mist Hashira—Muichiro Tokito—moved freely through the attacks of Uonuma Usui like an untouchable wisp of smoke.
"Damn it! Why can you dodge my attacks so easily?!"
Uonuma Usui was already covered in wounds, frantically stabbing in every direction with his short spear.
This location had been specially arranged by Nakime as his home ground. It blocked the vision of human swordsmen and naturally gave him the advantage.
Furthermore, after becoming a member of the Twelve Kizuki, he could merge his body into shadows, constantly appearing from unexpected locations.
Combined with the dim environment, it should have been an unstoppable strategy.
Yet his sneaky tactics of ambush and counterattack were completely useless against the agile Muichiro.
"Sorry... what was your name again?"
Muichiro's voice was cold as ice.
Mist Breathing: Fourth Form — Shifting Flow Slash
In that instant, the narrow corridor erupted with dense white mist so thick that even an outstretched hand could not be seen.
Although Uonuma Usui was blind, becoming a demon had granted him extremely powerful spatial perception.
But now, his senses sank into chaos.
He could perceive nothing.
He frantically swung his short spear, trying to disperse the mist.
However—
Within the fog, a ghostlike figure quietly passed by.
Slash.
The mist cleared.
Muichiro was already standing behind the Ten Blades warrior, slowly sheathing his sword.
"How... is this... possible..."
Uonuma Usui felt as though his throat had turned into a bubbling pool of blood as he collapsed to his knees.
Muichiro did not even glance back at the ashes behind him.
He simply touched his slightly swollen cheek, which was covered in cloud-like markings, and murmured softly.
"That direction... there's a very unpleasant presence. Is Asuka there?"
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