Kokushibo, now fully transformed into an ugly monster, catches a glimpse of himself in the reflection of Sanemi's blood-stained blade. What he sees is hideous—disgusting. For the first time in centuries, dread floods his heart.
Is this what I've become?
Was this the price of immortality?
His body begins to crumble. He no longer regenerates. Sanemi and Gyomei's relentless attacks tear him apart.
Then, he sees him—Yoriichi. Not the swordsman, but a child. Tears stream down Yoriichi's young face.
Kokushibo reaches out with a trembling, monstrous hand.
"Brother, it's over. Give up… Let's go. Wherever you go, I'll follow."
Kokushibo's body is nearly gone, reduced to crumbling flesh and drifting ash. In those final moments, he sees Yoriichi once more—his little brother, waiting with open arms.
But even now, he refuses.
He doesn't want peace. He wants power.
I want to live… to become the strongest…
In an instant, his body snaps back—regenerating faster than ever before. Flesh reforms, muscle tightens, and from his back burst four massive, writhing tentacles. With monstrous strength, he hurls Gyomei and Sanemi across the battlefield.
His six eyes blaze, locking onto them with inhuman fury.
His horns twist like a demon god's. His claws gleam like blades. Canines sharp as fangs stretch past his lips. The demon slayer mark spreads like rot across his entire body.
His eyes burn crimson.
Death has taken form.
Even an unborn child would die from seeing him now.
He's no longer Kokushibo. He's something worse—something even the Demon King might fear.
"Aah sh*t, he's regenerated his body," Sanemi shouts, bracing himself.
"Shinazugawa… I'm sensing something evil… Could it be—?" Gyomei's voice trembles.
Kokushibo unleashes a roar—so loud, so filled with rage, it shakes the Infinity Castle itself. Pillars shatter. The ground splits.
"We're too late," Gyomei whispers, pale with fear.
They lounge at him—
But Kokushibo vanishes—
In a blink, he reappears behind them, silent as a ghost.
"MOON BREATHING, THIRD FORM: LOATHSOME MOON CHAINS…"
Blades of slashing moonlight tear through the air.
Neither Sanemi nor Gyomei could react in time.
Blood splatters.
Sanemi's arms are severed in an instant.
"SHINAZUGAWA!!" Gyomei roars, eyes wide with horror.
Before Gyomei can reach him, Kokushibo moves again—
—A swift, clean strike.
Sanemi's head is taken, falls to the ground.
Gyomei doesn't hesitate. He charges, his chain and axe blurring through the air, forcing Kokushibo back.
For a moment, it feels like a true battle.
But it isn't.
Kokushibo deflects every strike effortlessly, overwhelming him with monstrous power.
"Tch… He's too strong. All I can do is defend", Gyomei thinks, gritting his teeth.
Kokushibo raises his blade, calm and merciless.
"MOON BREATHING, 16TH FORM: MOONBOW HALF MOON!"
Gyomei counters, unleashing his own strength:
"STONE BREATHING, 5TH FORM: ARCS OF JUSTICE!"
Their blades collide.
The impact is cataclysmic.
The ground explodes. The Infinity Castle groans and cracks. A storm of dust and debris engulfs the battlefield.
When the dust clears—
Gyomei is on his knees, weapon shattered, blood streaming down his face.
In less than a minute, the strongest Hashira is broken.
Kokushibo steps forward, his six eyes cold and pitiless. He lowers his sword to Gyomei's neck.
"So your name is Himejima?" His voice is cold, deep. "You had so much potential but… you're a pathetic human. Do you have any last words to say?"
Gyomei, bloodied but unbowed, glares up at him.
"One day… you'll pay for your sins," he says, voice steady. "You'll regret everything you've done."
Kokushibo's lips twitch—not a smile, not a frown.
Simply... silence.
"Is that so?" he murmurs.
With a flash of his blade, he decapitates his head.
Meanwhile—
Akaza and Douma had already claimed victory in their brutal battles.
Akaza stood over the broken bodies of Tanjiro and Giyu.
He had refused Koyuki's outstretched hand, choosing rage over redemption. Without hesitation, he slaughtered them both, severing their last hopes.
Douma, meanwhile, toyed with Kanao and Inosuke, laughing as he danced between them—freshly empowered after absorbing Shinobu.
But a sudden warning echoed in his mind—Muzan's voice.
"That butterfly girl has poisoned you… Kill these slayers right now… before it's too late!"
Without a shred of mercy, Douma struck.
Kanao and Inosuke fell, their blood staining the shattered ground. Shinobu's venom began to burn through Douma's body—but it was too late.
With a sickening crack of flesh and bone, he regenerated, laughing off the pain.
The tide had turned.
The Upper Moons stood undefeated.
The Demon Slayers had been wiped out.
…
A monstrous ripple tore through the Infinity Castle.
From a writhing cocoon of flesh and blood, the Demon King himself emerged.
Muzan's form was grotesque—mouths split across his body, hair snaking like tendrils, and thick tentacles writhing from his back.
He was no longer a man.
He was a force of extinction.
"Akaza… Douma… Kokushibo…" Muzan's voice rumbled, deeper than anything. "I am proud of you."
Douma clapped and twirled like a mad child. "Hahaha! Thank you, thank you, Muzan-sama!"
Then— the carnage continued.
Obanai and Mitsuri barely had time to raise their weapons before they were cut down without mercy.
Their deaths were swift. Almost meaningless.
"You've done well, my demons," Muzan said, gazing at his demons with cold satisfaction.
The era of Demon Slayers was over.
But…
Kokushibo stared at Muzan—
his six eyes wide with disbelief.
Something was wrong.
Terribly wrong.
"What's the matter, Kokushibo?" Muzan asked, his voice dangerously calm. "Why are you staring?"
Kokushibo clenched his jaw.
"Muzan-sama... the drugs," he said, struggling to stay composed. "They're slowing your regeneration… corrupting your cells. Little by little, they're poisoning you."
He hesitated before continuing, his voice dropping lower.
"At this rate… by tomorrow… you'll revert into a human."
A flicker of panic flashed across Muzan's face.
He reached out with his will… but nothing happened.
He could no longer read the thoughts of other demons.
He could no longer detonate their cells at a whim.
His power, once absolute, was slipping away.
"It can't be… which drugs did that b*tch use on me? Am I turning into a human?"
Muzan's pale skin grew even whiter. He stood frozen, swallowed by his nightmare.
Kokushibo, unsettled, asked carefully, "What's bothering you, Muzan-sama?"
For a long, suffocating moment, Muzan didn't answer.
Then—he moved.
Without a word, Muzan unleashed a storm of tentacles, surging at Kokushibo, Akaza, and Douma in a blur of monstrous speed.
Kokushibo sidestepped just in time, his instincts razor-sharp.
In a single, fluid motion, he countered—
"Moon Breathing: Sixth Form — Perpetual Night Lonely Moon!"
His blade carved through the air— slicing apart Muzan's tentacles and severing his right arm cleanly.
But Muzan regenerated instantly, flesh twisting and reforming before their eyes.
Muzan smiled—a hollow, dead thing.
"Nice move, Kokushibo," he said, voice low and hungry. "I always wanted to see your true strength."
Kokushibo narrowed his eyes.
"What happened to you, Muzan-sama?"
Muzan's smile twisted into a grimace.
"This body… It's finished. Tamayo's drugs... even I cannot heal completely."
His gaze sharpened, predatory.
"To survive… I must absorb one of you."
"As you wish, Muzan-Sama!," said Kokushibo, his voice hollow. "I've lost my purpose in life. My dream can never come true… Now I have no reason to live. Please, kill me and take my body."
Muzan's eyes slightly widened in surprise. "You would offer yourself so easily?"
He stepped closer, each footfall heavy, echoing like a death knell. "You could have sacrificed Akaza or Douma. Yet you choose yourself… Well done, Kokushibo.
At last, you're my only loyal demon."
Kokushibo knelt down, head bowed low. The air grew heavier—choking.
Akaza stiffened, his mind spinning. "Why Kokushibo? Why not Douma?!"
It hit them all in a single, sickening realization:
Muzan cared for no one. Not even his most faithful servants.
Muzan loomed over Kokushibo now, reaching out— fingertips just inches away from his skull.
Kokushibo's mind swirled with memories— a lifetime of battles, a mountain of corpses, a dream shattered.
"Is this what I fought so long for? To be absorbed like nothing?"
He saw Yoriichi's face behind his closed eyelids—
That same warm, blinding smile from centuries ago.
Rage and sorrow twisted inside him.
"I HATE YOU!!"
In a flash—
Kokushibo's hand tightened around his sword.
Steel screamed through the air.
SLASH—
Muzan's arm, his tentacles, even parts of his torso—sliced clean apart.
A heartbeat of stunned silence.
Everyone's eyes widened in shock.
Kokushibo now stood behind Muzan, his monstrous form shadowed in darkness—
his presence radiating pure, lethal intent.
For a moment—Muzan did not move.
Then, with a sickening crackle of bones and flesh, Muzan's body regenerated—within a microsecond.
He turned, crimson eyes blazing with murderous rage.
"I'LL KILL ALL OF YOU!!!" he roared.
The castle itself trembled.
Douma, unfazed as ever, clapped his hands lightly. "Oh my, seems like things are getting crazy," he chuckled.
"Shut Up, you b*tch. It's not a playground where you can play, if you won't fight back then all of us will be killed," yelled Akaza.
"Akaza-dono, that's so harsh."
Nakime doesn't know what to do, she's completely silent. Muzan has lost his control over her, and she is too inferior to even interfere.
Akaza and Douma squared their shoulders, readying themselves.
The air between them and Muzan burned with tension so thick it could snap.
Akaza clenched his fists, blood dripping from his knuckles.
"I apologize for this, Muzan-sama..." he muttered, eyes burning with resolve. "But survival comes first."
Without wasting a breath—
"DESTRUCTIVE DEATH: COMPASS NEEDLE!"
A shockwave rippled under Akaza's feet, the entire castle quivering under the technique's brutal force.
His fighting spirit blazed to its peak.
Douma laughed lightly, spinning his twin fans. "How tragic, Akaza-dono... It seems loyalty doesn't mean much in the face of death, does it?"
Muzan moved forward, slow and deliberate.
His monstrous form twisted—mouths gnashing, tentacles writhing like vipers ready to strike.
His eyes narrowed. "How pathetic, my demons. You're fighting me just to stay alive? Alright, then do your worst!"