Inside the Infinity Castle, chaos raged.
The air was thick with the power of monsters.
Akaza stood beside Kokushibo, both facing Muzan.
Tension clawed at the walls, reality itself trembling under the weight of their strength.
Muzan observes their every movement. "Exploding Kokushibo's cells would make the fight way easier. But… it's not easy to control him, especially when he's a complete beast.
I don't consider Akaza and Douma worthy enough to even fight me. I can squeeze them with my index finger alone."
Muzan's fist tightens, It's too risky... I'll have to solely focus on him. But if I fail here, all the demons will be freed from my control.
Gritting his teeth, Muzan lifted his hand toward Kokushibo.
In an instant, Kokushibo understood.
Without hesitation, he vanished from his spot—appearing directly in front of Muzan, sword already mid-swing.
"MOON BREATHING, NINTH FORM: WANING MOONSWATHS!"
A flurry of curved slashes spun out in an elegant, deadly dance, leaving arcs of glowing crescent blades in their wake—
Slicing off Muzan in no time.
Muzan regenerated the wounds instantly, his face twisted with rage.
He clenched his fist, aiming to rupture Kokushibo's cells from within.
Kokushibo staggered—his six eyes widening as invisible pain began to gnaw at him.
Muzan's arm shakes, unable to control him completely. Kokushibo pushes his limits, his muscles bulging.
But—
Before Muzan could finish, a frigid blast tore through the air.
Douma appeared beside him, his fans gleaming.
"Blood Demon Art: Scattered Lotuses!"
A flurry of razor-sharp snowflakes and glacial winds slashed at Muzan's body, tearing flesh apart.
Muzan snarled, leaping skyward with terrifying speed, evading the brunt of the attack.
Akaza vanished into thin air.
"DESTRUCTIVE DEATH: AIR TYPE!"
A sudden shockwave blasted through the battlefield—
Muzan's chest caved inward, ribs shattering with a sickening crack.
"Guh—BARRFFF—! What was that?!" Blood spewed from his mouth.
Muzan snarled, rapidly regenerating his crushed bones, landing hard onto the floor with a deliberate thud.
But his focus never wavered.
His right hand remained raised—locked onto Kokushibo.
Without warning, Muzan blurred forward, slicing the air with his blackened whips—aimed straight at Douma.
Douma only smiled, an eerie sparkle in his rainbow eyes.
"Blood Demon Technique: Hoarfrost・Waterlily Bodhisattva!"
A monstrous ice Bodhisattva erupted behind him, towering and divine. It swung its frozen arms, releasing gusts of deathly cold air, the kind that could freeze even blood mid-pump.
Muzan, with inhuman speed, vaulted into the air, narrowly dodging the devastating blast.
But before he could even breathe—
Akaza materialized midair, face-to-face with him.
"DESTRUCTIVE DEATH: ANNIHILATION TYPE!"
Muzan's six eyes widened in shock. When did he—?!
Akaza's fist, fueled by centuries of rage and power, drove into Muzan's face— striking the very spot Yoriichi Tsugikuni had once wounded four hundred years ago.
The impact was devastating.
Muzan's skull crumpled inward, his body smashing into the ground below, leaving a crater of gore and debris.
For the first time in centuries, he couldn't regenerate instantly.
His body twitched, struggling to rebuild itself—seconds felt like eternity.
And in that brief, fleeting moment—
Every demon felt it.
The chains of Muzan's curse shattered.
Kokushibo's blood boiled—his mind free for the first time in hundreds of years. Akaza and Douma sensed it too—their instincts no longer shackled.
Muzan, struggling to lift himself from the broken floor, spat a mouthful of blood, glaring at them with pure hatred.
"Tch... I shouldn't have underestimated you," he hissed, his voice dripping with venom.
Kokushibo's six predatory eyes locked onto Muzan— seeing straight through his flesh, peeling back layers of muscle and bone.
Seven hearts. Five brains.
A grotesque maze of organs, pumping unnaturally.
Yet even with the Transparent World at his command— Kokushibo couldn't find a true weakness. The vital points were blurred, shifting, protected by a sinister force.
A sudden thought came to his mind.
Kokushibo immediately turns to Akaza. "Akaza, I'll take the lead. Focus on attacking Muzan-Sama's weak points."
Akaza gritted his teeth, fists trembling with a bloodthirsty energy.
He gave a single, firm nod—eyes burning with determination.
———————————————————————
Meanwhile—
At the Ubuyashiki Mansion, a heavy, suffocating silence gripped the halls.
The air was thick with sorrow, and the walls seemed to groan with grief.
Oyakata-sama—so often a figure of calm wisdom—now sat crumpled in his chair, his face buried in his hands, sobs wracking his frail body.
His followers and caretakers knelt beside him, trying to soothe him with trembling voices.
"How did this happen?" Oyakata-sama wept, his voice raw and broken. "Despite everything we sacrificed... everything we endured... we still lost..."
Tears streamed down his hollowed cheeks.
Across from him, Shinjuro Rengoku—Kyojuro Rengoku's dad—could barely keep himself upright.
"Kyojuro... I'm sorry, my son," Shinjuro choked out, his voice shattering mid-sentence. "We failed to avenge you. I failed you..."
Beside him, Tengen Uzui sat frozen, his flamboyant spirit extinguished. He stared vacantly at the ground, unable to speak, unable even to mourn properly.
The wounds ran too deep for words.
…
In another corner of the mansion, Nezuko slept quietly.
Her transformation back into a human was nearly complete.
But deep within her dream, a figure emerged from the mist— Tanjuro Kamado, her father. His face, once warm and gentle, was now filled with sorrow.
His voice, soft and brittle, barely reached her. "Nezuko... your brother... he's gone. He won't come back."
Nezuko's eyes snapped open.
Without a second thought, she bolted upright and ran— her bare feet pounding against the wooden floors, her heart screaming louder than any words could.
"Nezuko?!" the others called after her, panic rising.
Sakonji Urokodaki lunged to intercept her, but she was too fast.
Oyakata-sama struggled to rise, but—
A ghostly hand, glowing faintly, touched his shoulder.
Kagaya Ubuyashiki.
The soul of the former leader whispered to him with a soft, knowing smile:
"Let her go. She'll be alright."
[Author's Note: Nobody will point out about soul interaction as this is a canon scene of the manga.]
Nezuko sprinted faster, breathless, until she reached the edge of a great cliff.
Before her—only endless mist and a deadly drop.
But then—
She saw it.
Her father's spirit, standing at the edge, pointing downward.
"This way," he seemed to say.
With a leap of desperate faith, Nezuko jumped.
[A/N: Again, this is a canon scene. I didn't cook this one.]
Sakonji skidded to a halt at the cliff's edge, watching helplessly as she vanished. He clenched his fists but... he let her go. There was nothing more he could do.
Nezuko ran and ran through the hidden paths that twisted beneath the earth. And with every step, memories flooded back into her mind—
flashes of blood, fangs, and claws. The nights she had almost lost herself. The countless times her brother had protected her, carried her, believed in her.
Tanjiro...
She had become human again because of him.
And now he was... gone?
She couldn't accept it. She wouldn't. Not without seeing it herself.
Nezuko stumbled forward, her tears blinding her, until—
A figure materialized before her.
Yushiro.
"Nezuko..." he said gently, relief flooding his features. "I'm so glad to see you back... as a human."
Nezuko clutched at his sleeves, her voice breaking. "W–Where's Onii-chan?!"
Yushiro's face darkened. He lowered his gaze, unable to meet her eyes.
Behind him, another figure staggered forward—
Zenitsu.
His golden hair was matted with sweat and dirt. Tears streamed down his battered face.
"N... Nezuko-chan..." he croaked. "Please... calm down... Your brother… Tanjiro..."
His voice splintered. "He's... gone."
The words hit her like a blade to the heart.
Yushiro placed a hand on her trembling shoulder, his own voice filled with regret:
"Zenitsu is right... Only the two of us survived. Everyone else... Even Tamayo-san... They're all gone."
Yushiro's voice cracked when he spoke Tamayo's name, and for a moment, he too looked as if he would collapse under the weight of grief.
———————————————————————
Now
In the Infinity Castle.
Akaza and Douma have been rendered unable to fight as they have been sliced into countless pieces. And demons being unable to kill each other, they must either be absorbed by a stronger demon or be unable to regenerate.
Their regeneration slowed down.
Kokushibo glares at Muzan, his eyes burning with menace, glowing dark golden.
Second drug has now affected Muzan, causing him to become weaker than before.
Muzan looks at Kokushibo, his eyes widened. He resembles something terrifying… He looks identical to Yoriichi now.
"Is this… that man? No, it can't be… Even if they're twins, there's still a huge power gap between them. This is not Michikatsu, or that man, this is my Kokushibo," thinks Muzan while shivering.
The crimson blade of Kokushibo's sword, Kyokokukamusari, radiates a fierce red glow, casting an ominous light on the battlefield. His piercing gaze, filled with malice, is fixed upon Muzan.
In this moment, he seems to eclipse even the dread presence of the Demon King himself.
"So you're the one who fought Yoriichi, Kibutsuji Muzan," Kokushibo's voice is dark, cold.
Muzan is overcome with a sensation akin to icy tendrils trailing down his spine, every fiber of his being quivering with inexplicable dread. It feels as though his very soul is besieged by the force of seven simultaneous heart attacks.
In that harrowing instant, he perceives Kokushibo as an embodiment of Yoriichi himself.
"This guy again… is this… a nightmare? I can't even move an inch, it's not Kokushibo. Wait, is that.. that guy?"
"MOON BREATHING 6TH FORM: PERPETUAL NIGHT LONELY MOON!"
Kokushibo rapidly performs a multitude of curved slashes several meters in front of him that releases a wild barrage of crescent moon blades.
Muzan didn't dodge the attack. His body, usually capable of instant regeneration, was now unable to heal some of his body parts, including his head.
"What?!! What just happened? He targeted my weak spots," thinks Muzan.
Struggling to regenerate, Muzan hadn't absorbed Akaza or Douma yet due to Kokushibo's interference. Despite this, he managed to grow even deadlier whips from his thighs.
His whips move even faster than anything, causing a huge storm in the Infinity Castle.
Kokushibo stays on his ground, and doesn't flinch even a bit.
Finally, Akaza and Douma fully regenerate themselves, now facing Muzan along with Kokushibo.
Akaza's compass needle has undergone a remarkable improvement, allowing him to not only react to Muzan's attacks but also launch counterattacks alongside Kokushibo.
[The Compass Needle Technique evolves during the intense battle, boosting defense, reaction time, and precision.]
Their earth-shattering shockwaves are laying waste to the entire Infinity Castle, but Nakime is working to rebuild it at an incredible speed, even though her pace can barely keep up with the destruction.
One hour later, after a continuous fight, the third drug has affected Muzan now. He understands that he can't win against the Upper Moons in this state. He has become much weaker than before.
Muzan is lying on the ground, and Kokushibo is standing in front of him, much like how Yoriichi was standing in front of Muzan.