At that moment, Kibutsuji Muzan—who was being solo-tanked by the Hero of the Shield's Heavy Bowgun—roared from the heart of Infinity Castle:
"KOKUSHIBO! NAKIME!! WHAT ARE YOU STILL DOING?!!! MOVE, NOW!!!!!!"
Meanwhile, Kokushibo himself had grown mentally frazzled.
Just facing the four Hashira was already immense pressure—
But now there was Kairo Retsu, who had been trying to unsettle him from the start.
Kokushibo desperately wanted to calm down and fight rationally.
Yet Kairo's words wormed into his mind—he couldn't not care.
Or rather...
Once anything involving Yoriichi was brought up—those emotions, long buried, began to erupt like a boiling geyser.
To make matters worse, Muzan's cells inside his body wouldn't stop pressing him:
"Kokushibo! End the fight! Come here now!!!!"
Muzan's furious commands echoed ceaselessly in his head.
Blue veins throbbed on Kokushibo's forehead—but he simply couldn't break free from their coordinated assault.
This mental state…
Caused something to appear on Kokushibo's head—something only Kairo Retsu could see:
A very familiar red rage mark, in the shape of a glowing eye.
"Crap! He's enraged! Can't wallbang now! Watch out, everyone—he's entered Phase Two!!"
Kairo's shout rang out across the entire battlefield, loud and clear for all to hear.
It only made the veins on Kokushibo's head bulge even further.
This abnormal entity…
Could he really not see the Transparent World that Kokushibo saw with such clarity?
Then how was he so keenly aware of Kokushibo's internal emotions?
Or…
Was it perhaps a different "world" entirely—one Kokushibo could never reach no matter how far he chased?
If he could see emotion like this…
Would he finally understand what Yoriichi—the one who transcended this world, beloved by the gods—was truly thinking?
The thought twisted Kokushibo's expression.
And with that shift in his mind—his body also began to change.
Where once he resembled a human aside from his extra eyes, now he grew—
Swelling to over three meters tall in mere seconds.
His once-Yoriichi-like face mutated, disfigured by his transformation.
All six of Kokushibo's eyes now locked furiously onto Kairo Retsu—
So intensely that even Kairo, mid-shout, felt a chill run down his spine.
"KAI—RO—RE—TSU!!!!!!!"
Kokushibo roared, his flesh-made greatsword swelling with him—
He swept away both Tengen Uzui and the Wind Hashira in one fell strike.
Then—
He drove the blade directly into his own brain.
"Kokushibo!!! Kokushibo!!! Koku—"
Inside his mind, Muzan's incessant shrieking abruptly ceased.
At last, Kokushibo could focus entirely on the anomaly before him.
"Tell me everything you know!!"
He bellowed, ignoring the others entirely, charging straight toward Kairo Retsu.
Kairo watched Kokushibo barrel toward him, blinking wide in confusion.
Why the heck was Kokushibo going into full Berserk Mode out of nowhere?
…Okay, maybe he had said quite a lot of things to provoke him.
In hindsight, the guy holding out this long before snapping was kinda admirable.
"Not bad, Kokushibo! You held your temper all the way till now! I respect that!!"
Kairo shouted back at the towering demon, who now wielded a bloodflesh sword as large as a Wyvern Blade.
"But did you really think we didn't prepare for this?!"
Kairo yanked at his collar, revealing a necklace hanging from his neck, and popped a red pill into his mouth.
"Let me show you what it means to be a hunter!"
"When we know what monster we're hunting—
We come prepared!!"
Rather than evade, Kairo charged straight in.
From his backpack, he pulled out a jet-black armor set and threw it on mid-run.
"Kono… Challenger Charm—DA!!"
Even as Kairo shouted his nonsense, Kokushibo closed the distance, towering over him.
From above, Kokushibo raised his massive fleshy blade—unleashing a sword technique with full intent to kill.
He believed—no, knew—this hit would land.
Kairo was human. No matter how strong, he could never match a demon in a head-on clash.
But then—
Kokushibo's eyes caught it.
The necklace on Kairo's chest burst into a blinding red light—
That light surged through his entire body.
At that exact moment, Kairo crushed the red pill between his teeth.
"Let's go—a proper blade duel!!"
The two colossal weapons clashed—
In the very first exchange, Kokushibo's flesh-forged greatsword was nearly cleaved in two.
His eyes widened.
Kairo's offense had suddenly become terrifyingly sharp.
There was no change in muscle structure. No enhanced physique.
But his attacks—were now exponentially more lethal.
[Challenger Charm: When the monster is enraged, Attack and Affinity increase.]
[Might Seed: Greatly boosts Attack for a short duration.]
"Let's keep swinging!!"
Kairo's face was alight with glee.
"Time to show you what Heaven's Wrath looks like!!"
"ROAAAAAAAAAARRRRRR!!!!"
Kokushibo's fury exploded—
Countless blades sprouted from his body, slicing everything around him to shreds.
These slashes were so ferocious that the other Hashira couldn't even approach—
They could only watch in horror as Kairo was engulfed by the bladed storm.
Kokushibo, now wielding a regenerated greatsword, brought it down on Kairo with full strength.
No matter how monstrous this man was—he refused to believe anything could survive this kind of assault.
But—
Amidst the whirlwind of slashes, what scattered wasn't flesh—
—but a few harmless sparks.
And standing right in the center of the maelstrom—
Was Kairo Retsu, completely unharmed, sword glowing red, slashing straight into Kokushibo's flesh.
Like a motionless mountain deity—
"IMMOVABLE ARMOR!!"
"YA LITTLE PUNK!!!!"