The air was dense, almost suffocating, as though the atmosphere itself had grown heavy with dread, deep within the fractured remnants of the Infinity Castle, a monstrous cocoon pulsated with malevolent energy. The flesh-like shell writhed and quivered, glowing faintly as if something unspeakably powerful was about to emerge.
The surrounding Demon Slayers, mere remnants of the once-mighty corps, stood in tense silence, their weapons drawn and their bodies trembling with a mix of fear and determination. The cocoon suddenly split with a sickening squelch, sending streams of black and red ooze spilling onto the shattered floor.
From within, Muzan Kibutsuji emerged.
Muzan stepped forward, his unnaturally pale skin glistening in the dim light. His once-curly black hair had turned stark white, flowing down his back like a ghostly cascade. His sharp, almond-shaped eyes, now a vivid crimson, glowed with an otherworldly menace. His limbs were lined with grotesque mouths, each one filled with jagged teeth that clicked and hissed hungrily. The dark-red mass that branched from his limbs pulsed like a living organism, exuding an aura of overwhelming malice.
His gaze swept across the battlefield, disdain flickering in his crimson eyes. "Ants," he muttered, his voice low and venomous. "This... is all that remains of your pathetic rebellion?"
Without warning, Muzan moved.
The speed was incomprehensible. One moment he was standing in place, the next, he was amidst the Demon Slayers. A blur of claws and mouths followed, leaving a trail of devastation in his wake. Screams filled the air as limbs and torsos were severed, blood spraying like a macabre fountain.
From the shadows, Giyuu Tomioka appeared, his Water Breathing sword raised high. The mist of blood hadn't even settled before his blade arced downward, aimed at Muzan's neck.
Muzan blocked effortlessly, one of the mouths on his arm biting down on the blade with a metallic screech. "Ah, the Water Pillar," Muzan said mockingly. "Still alive. Impressive, but ultimately futile."
Giyuu's expression remained stoic, his blue eyes burning with resolve. He twisted his blade free, delivering a rapid succession of strikes that forced Muzan back. Each move was precise, deliberate, but Muzan's regenerative speed made every cut meaningless.
Moments later, Shinobu Kocho darted into the fray, her diminutive form a blur of speed. Her Nichirin sword, coated in deadly poison, aimed for Muzan's exposed limbs. "You're not invincible," she hissed, her voice sharp and cutting. "You can be killed!"
Muzan swatted her aside with a single strike, sending her crashing into a wall with a sickening crunch. Before he could follow up, Inosuke Hashibira and Kanao Tsuyuri charged in together, their blades slicing through the air in synchronized arcs.
From a distant corridor, the sound of footsteps grew louder. Bell emerged first, his demeanor calm and composed, as though the chaos before him was nothing more than an annoyance. Behind him, Gyomei Himejima and Tanjiro Kamado followed closely, their expressions grim as they took in the massacre.
Bell's gaze settled on Muzan, his crimson eyes narrowing slightly. "So, this is the King of Demons," he said, his voice carrying an edge of amusement. "Quite the temper tantrum you're throwing."
Tanjiro's hands tightened around his sword. His face was pale, but his resolve was unshaken. "He's... stronger than I imagined," he murmured.
Gyomei rested his massive flail on his shoulder, his blind eyes fixed in Muzan's direction. "Bell," he said calmly. "Are you certain you don't need our help?"
Bell glanced back at the two of them, a faint smirk playing on his lips. "Stay back for now. He's not even interesting yet."
Muzan's attention snapped to Bell, his crimson eyes narrowing in contempt. "Another arrogant human," he said, his voice low and deadly. "Do you think you're the first to challenge me?"
Bell shrugged, his tone casual. "No. But I'll be the last."
Before Muzan could respond, the sound of reinforcements echoed through the broken hall. The remaining Pillars arrived, their presence a wave of steel and determination. Mitsuri Kanroji, Obanai Iguro, Sanemi Shinazugawa, Tengen Uzui, and Muichiro Tokito joined the fray, each one ready to lay down their lives if it meant defeating the King of Demons.
From another entrance, Shinjuro Rengoku, his once-broken spirit now reignited, arrived alongside Zenitsu Agatsuma. The Thunder Slayer's eyes were wild with fury, his breathing ragged as he gripped his sword tightly.
Zenitsu's gaze landed on Muzan, and his body trembled—not with fear, but with rage. "You...," he muttered, his voice shaking. "You're the reason for all of this."
Muzan chuckled darkly. "Ah, the insects keep gathering," he said. "Good. I'll crush all of you at once."
The slayers formed a loose circle around Muzan, their blades glinting in the dim light. Injured and battered, they stood together, united by a single purpose: to bring down the King of Demons once and for all.
Bell stepped forward, his smirk widening into a feral grin. "You wanted a fight, Muzan? You've got one."
The demon's monstrous form shifted slightly, his grotesque mouths curling into something that might have been a smile. "Foolish humans," he said softly. "You've only hastened your demise."
With a deafening roar, the battle began.