The central dojo of the Infinity Castle.
The battle between Taka and Kokushibo had also entered its final, life-or-death sprint.
"Caw—!! Caw—!!"
"Agatsuma Zenitsu! Upper Rank Six! Defeated!!"
'Success? That crybaby.'
The Kasugai Crow's message came through. The thunder over where Zenitsu was had already subsided, causing Taka's originally tense nerves to relax slightly.
This momentary looseness allowed Kokushibo to seize an opening.
[Moon Breathing: Moonbow, Half Moon]
The massive grotesque blade brought down several rainbow-like slashes from the sky, each moon shadow enough to cleave through multiple platforms and buildings.
Taka quickly blocked, but those fragmented moon blades, as if possessing self-awareness, circumvented his defenses and sheared off a large piece of flesh from his left shoulder.
"You were distracted." Kokushibo's six eyes were now cold as a god's. "Under my blade, any distracting thought is fatal."
"Heh, that's not necessarily true."
A faint smile curled at the corner of Taka's mouth.
"Haven't you noticed it yet?"
"What?"
Prodded by him, Kokushibo felt an immediate sense of unease in his heart.
With prolonged contact between the Zanpakuto and the opponent's demonic blade, Tonan's greedy Reiatsu had begun to penetrate deep within.
The eyeballs on Kokushibo's grotesque blade were turning dim, one after another.
"Your Zanpakuto... seems to be getting eaten by me."
"And honestly, if it weren't for you hard-to-kill Kizuki, I wouldn't know who to test such an ability on...."
"Tear apart, Tonan."
"What are you saying?"
Seeing Taka's momentum change, Kokushibo immediately sensed something was wrong.
'This kid still had a trump card? Sun Breathing, Crimson Blade, and the Demon Slayer Mark still weren't his limit?'
'What exactly was he?'
During these days... even earlier than that, Taka had been pondering the development of his Zanpakuto's abilities.
He couldn't pinpoint the limits of Tonan, and no one could teach him.
He now clearly knew of three abilities.
Howling, Roaring, and Tearing.
These were names he had randomly shouted out based on his inner emotions, now deeply bound with his Zanpakuto.
In its Howling state, the Zanpakuto could slash out packs of vicious dogs composed of his internal Reiatsu.
These Reiatsu beasts were almost uncontrollable by Taka, only able to bite in a predetermined direction, sometimes even attacking each other.
But fortunately, damage to them did not affect Taka. They were his primary means of probing and restraining enemies.
The Roaring state of Tonan was even more extreme, only usable when Taka's emotional reaction was intense and he had an extremely strong desire to fight.
The Zanpakuto would compress Reiatsu, slashing out black-red strikes that carved deep ravines into hard mountain rock.
The power was sufficient, the destruction strong. The only drawback was that its speed was somewhat slow, giving enemies time to react.
As for Tearing... it was a technique Taka had comprehended only recently, after integrating the five Breathing Styles.
And now was the time to verify it.
"What do you feel inside right now? Pain? Stagnation? Or just numbness?"
"Absolutely ridiculous!"
Kokushibo swung his blade again, but Taka did not counterattack, using agile body techniques to evade his attacks.
He looked seriously at Kokushibo: "If you don't tell me, how will I know if it's working? How will I improve the technique?"
"Be silent!!"
Kokushibo wasn't unaware; he already realized the situation was bad.
Waves of power not his own were rushing wildly through his body.
The feeling of this power was very similar to the flames that had burned on his body and sword before, yet completely different.
They were minute yet tenacious. Kokushibo countless times tried to use his demonic power to devour this force, but it always slipped away.
Even if he tore open his own skin, ripped off his own flesh, these little things still relentlessly bored into his body, refusing to come out!
"You're unwilling to say, but I can roughly sense it."
"I changed my approach, splitting Tonan's Reiatsu into many small portions, infiltrating them into your body through every exchange."
"Once or twice, you wouldn't notice. But by the time you did, Tonan's power would already be permeating your entire body."
"According to Shinobu, this is called a virus."
Taka dodged another enraged Moon Breathing slash and explained expressionlessly, also organizing his own thoughts.
He pointed at Kokushibo's waist and abdomen, which had already begun to fester, and spoke with a probing tone: "See, the virus is already taking effect."
"Shinobu's fighting style has value. Sometimes it's not just about overpowering the enemy; gaining advantage in the subtle details is also important."
"You despicable fellow! Poisoning in a swordsman's duel!"
Kokushibo was furious. He slashed apart his own rotting wound, trying to use his regenerative ability to grow anew, but the virus had already spread.
Tonan's Reiatsu rampaged through his body, breaking down his Muzan cells from the inside out.
'Despicable? Don't be ridiculous. You're a demon.'
'If it can kill a demon, then this is a righteous poison blade.'
The starving dogs formed from Reiatsu would not miss any opportunity to devour and seize flesh and blood. Even if beaten away with clubs, even if fought by companions, they would grit their teeth and persevere to the very last moment.
One or two might be insignificant, but when they gather in force, and the Reiatsu within the body is completely detonated by Taka, such destruction is enough to disintegrate any enemy from within!
Not to mention, Taka's swordsmanship was not lacking either.
"Sky Rending!!"
The Zanpakuto slashed down through the air. Kokushibo could only barely parry while enduring the festering of his flesh.
His movements began to grow slower and slower, his openings wider and wider!
At this moment, he suddenly felt the crisis of death.
He thought back to hundreds of years ago, when he was still human, still named Tsugikuni Michikatsu.
"The passing down of Breathing Styles is despairing. To this day, there is still no swordsman who has mastered and integrated Sun Breathing."
"The Demon Slayer Corps has no swordsmen who can reach our level. If we die, what then?"
"At this rate, the painstakingly nurtured ultimate techniques will be lost."
Michikatsu stroked his Nichirin Sword, his brow deeply furrowed, anxiously looking at the tall man before him wearing sun-shaped earrings.
The man turned around, his expression calm, seemingly unconcerned: "Brother, you worry too much."
"You think too highly of us two brothers. We are merely two passing travelers in the long history of humanity...."
"An infant with talent far surpassing ours might be being born somewhere right now. Someone will eventually reach our level."
Yoriichi looked at the distant sky and smiled contentedly: "We only need to let things take their natural course and await the day our lives draw to a close...."
Even centuries later, Kokushibo clearly remembered these words.
'Yoriichi, every time you smile, I feel immensely disgusted.'
'How could anyone possibly surpass us? How could anyone possibly learn Sun Breathing?'
But now, Kokushibo's six eyes fixed.
Taka's blade was invasive as fire, moving with the force of thunder. Every strike carried a blazing sun wheel, pressing against Kokushibo's blade, making it difficult for him to cope.
The person his brother spoke of had truly appeared.
Pffft—!!
His chest was slashed open. The scorching heat of the Crimson Blade prevented his regeneration. The virus within was destroying his internal bones!
This reminded Kokushibo of that night.
When, after becoming a Kizuki, he faced his already aged and dying brother, Yoriichi—
That extreme sense of powerlessness.
"Don't be ridiculous! I am the strongest swordsman! The strongest Kizuki!!"
Kokushibo roared. The demonic power within him emitted an intense resonance.
The slashed skin began to grow and distort unnaturally fast. Flesh covered in barbs rapidly filled the gaps.
Not only that, his severed arm transformed into ferocious joints like those of an arthropod. His split skull grew terrible twisted horns.
In no time, the battered Kokushibo had completely transformed, losing all human form.
Whether he became stronger now was debatable, but he had certainly become uglier.
Taka looked at the ugly posture of Kokushibo, still struggling to survive even in this state, and for the first time, sighed at an enemy:
"Tsugikuni Michikatsu, I'm here."
At these words, Kokushibo only felt his entire body turn cold, as if already condemned to death.
'So fast! Why was his speed so fast!'
'No, it was I who became slower.'
Using the reflection from the flickering pavilions within the Infinity Castle, he saw his own ugly visage.
He froze.
Neither man nor demon, completely a monster composed of twisted joints and mangled flesh, only struggling to survive under Taka's power.
'Was this ugly form the realm I desperately sought to achieve?'
'Was it for something like this that I lingered on for centuries?'
'How ridiculous.'
Sizzle—!!
Taka's Crimson Blade radiated high heat, slashing into Kokushibo's twisted, thick neck, emitting the sound of oil frying meat.
Shing—!
The next second, the scorching blade severed Kokushibo's head.
And shattered his final memories.
A small Yoriichi held a bamboo flute, showing him a happy smile.
His little mouth moved, but Kokushibo could not hear what he was saying.
"I merely wished to be the moon that becomes the sun....."
The ugly head turned to ashes and scattered.