Author's Note:
This chapter will focus solely on the events unfolding within the Infinity Castle. The main character (MC) will not appear in this chapter.
And thank you :-
dreamer_0901, enzo_morninhstar, the_racist_one (well quite a name) and all other who give power stone well I don't want to be like other writers who open patreon i just write when I like.
````````````````````````````````````````
INFINITY CASTLE
THIRD PERSON POV
Ten minutes earlier, the Infinity Castle's upper chambers were a battlefield of ruin, the air thick with dust and the acrid scent of blood.
Shattered beams hung precariously overhead, their splintered ends swaying in the faint breeze. Flickering torchlight cast long, wavering shadows, turning the space into a haunting tableau of war.
Sanemi, Giyu, and Tanjiro fought Kokushibo with everything they had, their bodies battered, their spirits stretched thin.
Sanemi's scars were slick with sweat, his grin wild and unhinged as he swung his blade, his eyes blazing with defiance.
"This bastard's cheating! Damn it!" he snarled, his voice rough with frustration, his shoulders heaving as he circled for an opening.
Giyu's calm facade was cracking, his lips pressed tight, his eyes burning with a fierce determination that belied his quiet nature.
Tanjiro's forehead mark pulsed in time with his heartbeat, a steady rhythm that echoed like war drums within his skull. His face was etched with unwavering resolve, every breath sharp and focused, honed like the edge of his blade.
The clash of steel rang out again—Kokushibo's monstrous blade met theirs, a storm of sparks igniting the darkened chamber. Giyu stood silent and composed, his movements fluid like water. Sanemi grunted, his face twisted with effort as he wiped sweat from his eyes.
Their arms trembled from exertion, muscles screaming for rest, but still, they stood.
Unbeknownst to them—something had changed.
A ghostly mist had begun to gather on Giyu's cheeks. A red, flame-like sigil danced atop Tanjiro's brow, glowing brighter with every heartbeat. And on Sanemi's cheeks, a windmill-like mark had begun to shimmer beneath the sweat and blood.
"Is it just me… or is it hot in here?" Sanemi muttered, his voice low, confused.
His eyes flicked to Tanjiro and Giyu. He could feel it—their bodies radiating heat, not from the battle alone, but from something deeper. A fire not of muscle or breath… but of fate.
And then, like a lightning bolt from the past—Alex's voice returned to them, echoing in the hollows of their minds from a long-ago training session:
"When a Demon Slayer reaches the peak of focus in battle, rare phenomena occur."
"Heart rate exceeds 200 beats per minute. Core body temperature rises to 39°C."
"You'll unlock more than strength or speed. You'll gain access to the Transparent World... and the Demon Slayer Mark will appear on your body."
"But beware—this power has a cost. It burns your life force. If these symptoms arise... drink the low-end potion. It'll help bypass the side effects without breaking your flow."
The memory struck them all at once.
Tanjiro's eyes widened. "Potion. Now," he whispered, his voice urgent but steady. The three reached for their vials, their movements synchronized despite their exhaustion.
They drank, the liquid burning down their throats, and the effect was immediate— wounds closed and pain dulled. Tanjiro's shoulders straightened, his eyes blazing with renewed fire. Giyu's stance steadied, his jaw unclenching as he wiped blood from his chin.
Sanemi tossed his vial aside with a snort, his grin returning. "Hey, you demons regenerate every damn second. This? This is just balancing the scales, you smug bastard," he taunted, his voice dripping with bravado.
Kokushibo's six eyes narrowed, his lips twitching with disdain. "You resort to alchemy now?" he said, his voice calm but edged with scorn. His posture remained unyielding, his blade gleaming with malevolent intent.
The castle convulsed as Kokushibo raised his sword.
"Blood Demon Art – Moonlit Void Field," he intoned,
his voice like a death knell. A shimmering dome of warped space erupted, laced with crescent slashes that spun in chaotic orbits.
The air crackled, the floor fracturing under the onslaught. Giyu's eyes widened, his voice sharp. "Don't step wrong!" he barked, his body tense as he tracked the deadly arcs.
Tanjiro moved first, his blade glowing like a rising sun. "Hinokami Kagura – Thirteenth Form!" he shouted, his voice ringing with conviction.
His movements were a dance, threading through the chaos with impossible grace, his body leaving afterimages in its wake. Each slash forced Kokushibo back, just a half-step, but it was enough.
Giyu struck next. "Water Breathing – Eleventh Form: Dead Calm!" he called, his voice steady as he stood still, the chaos pausing around him. The crescents hesitated, caught in his serene aura, and for a moment, reality held its breath.
Sanemi seized the opening. "Wind Breathing – Ninth Form: Gale – Sudden Gusts Barrage!" he roared, dropping from above like a howling storm.
His blade spun with furious velocity, each slash tearing through the stillness Giyu had created.
A deep wound ripped across Kokushibo's chest, and the demon staggered, his breath uneven, his eyes narrowing in surprise.
But Kokushibo's body writhed, the gash closing in seconds. "You're… persistent," he said, his voice still maddeningly calm.
"You are not him," he added, his gaze locking on Tanjiro, "but you carry what he left behind. A will stronger than steel…" His lips twitched, a flicker of respect breaking through his icy demeanor.
Tanjiro surged forward, his eyes blazing. "Hinokami Kagura – Sunflower Thrust!" he shouted, his blade igniting the air with radiant heat.
Every form of Sun Breathing flowed seamlessly—Dance, Flash Dance, Flame Flow—each cut faster, heavier, burning his lungs from within.
Giyu and Sanemi struck in unison, their attacks perfectly timed. Giyu's stillness opened a crack in Kokushibo's defense; Sanemi's wind forced him off balance. They had created this moment for Tanjiro.
"Hinokami Kagura – Burning Bones!" Tanjiro roared, launching into the air, his body spinning like a blazing comet. His blade came down in a perfect arc, severing all six of Kokushibo's eyes in one devastating strike.
KRRRRRSHHH! The sound was like glass shattering, and Kokushibo's head flew free, crashing through a shattered window into the void beyond. His body trembled, then collapsed in a heap.
Silence fell, heavy and ringing. Tanjiro dropped to his knees, sweat streaming down his face, his breath ragged. His blade sank into the ground, his hands trembling with exhaustion.
Giyu wiped his katana clean, his expression unreadable but his shoulders sagging with relief. Sanemi blew a damp strand of hair from his face, his grin crooked and wild.
"Well… that was intense… but I've had worse hangovers," he panted, his voice laced with dark humor.
Tanjiro let out a tired chuckle, and even Giyu's lips twitched into a faint smile, the tension breaking for a fleeting moment.
BOOOOM!
The castle trembled, a shockwave shattering the fragile peace. Debris rained from the ceiling, dust choking the air. Tanjiro, Giyu, and Sanemi turned toward the source, their eyes wide with alarm.
Far below, a crater had blasted open in the ground, and within it stood Muzan Kibutsuji, his pale form radiating malice. His crimson eyes gleamed, his lips curled into a cruel smile, his posture relaxed but predatory, like a lion toying with its prey.
Before him stood four warriors—Shinjuro Rengoku, Sakonji Urokodaki, Gyomei Himejima, and Obanai Iguro. Their faces were weathered, their bodies scarred, but their stances were unyielding, their eyes burning with defiance.
Tanjiro's heart lurched. "We have to help them!" he shouted, his voice raw with urgency. He sprinted forward, Giyu and Sanemi following without a word, their exhaustion burned away by a single purpose.
Elsewhere, Zenitsu's ears twitched at the tremor, his face paling. "That sound…" he muttered, his eyes narrowing.
He turned, not toward Muzan, but in the opposite direction. "That biwa demon… she's still playing that shamisen. We won't get out of here unless she's stopped." His voice was firm, his earlier fear replaced by resolve.
Cara and the SPADE Unit nodded, their movements synchronized. Zenitsu shouted, his legs already moving, his blade crackling with residual electricity.
```````````````````````````````````
THIRD PERSON POV(few moment before the BOOOOM sound)
The deepest chamber of the Infinity Castle was a cathedral of horror, its vaulted ceiling dripping with crimson ichor. The walls shimmered with a sickly glow, their surfaces carved with grotesque faces that seemed to writhe in agony.
The air was stifling, thick with the scent of decay and the faint twang of Nakime's biwa, its notes warping the space around them. Shattered platforms floated in the void, connected by twisting bridges that defied logic.
"Muzan-sama… four intruders have bypassed all the demons and are approaching this direction," Nakime said
Her voice calm as she plucked her biwa's strings. Her pale fingers moved with eerie precision, her single eye unblinking, her posture serene despite the chaos.
Muzan stood on a balcony-like platform, his crimson eyes half-closed in amusement, his lips curled into a faint smile. The screams of battle were music to him, but Nakime's words soured his mood. His smile faded, his shoulders tensing as he rose, his cloak whispering against the floor.
"These vermin really do know how to crawl under my skin," he muttered, his voice dripping with venom. "Use your demon art, Nakime. I'll deal with them personally." His eyes burned, his steps echoing with predatory finality. "And protect yourself. If you fall… the castle falls with you."
Muzan launched himself into the void, a black meteor crashing through the air. BOOM! The shockwave rippled across the battlefield, and the four Hashira—Shinjuro, Sakonji, Gyomei, and Obanai—skidded to a halt, their instincts flaring.
Smoke and debris clouded their vision, but Obanai's senses caught the bloodthirst in the air. His blade flashed, deflecting a tentacle-like appendage that shot through the mist.
The force sent him skidding back, his boots grinding against the stone, his arms trembling. His eyes widened, his breath hitching. "That… thing. That wasn't just speed," he muttered, his voice tight with alarm.
Muzan emerged from the smoke, a cold and menacing smile on his face. His posture was relaxed, yet he radiated danger. His crimson eyes gleamed, and his hands were clasped behind his back, as if he believed the fight was already won.
"Now, without any futile attempts, can you tell me where that girl and the Ubayashiki family are?" he asked in an authoritative tone.
The Hashira gasped, their faces paling as they confronted the architect of a thousand years of bloodshed.
Shinjuro's jaw clenched, his eyes blazing with old wounds. Sakonji's mask hid his expression, but his hands tightened around his blade, his stance steady.
Gyomei's lips moved in silent prayer, his massive frame unyielding. Obanai's eyes narrowed, his body coiled like a serpent ready to strike.
"wrong answer"his voice cold devoid of any emotion
Muzan moved without warning, his body exploding into motion. Tendrils lashed out, each one a supersonic whip that shattered the ground.
Gyomei reacted first. "Stone Breathing – Third Form: Stone Skin Rampart!" he roared, smashing his flail into the ground. A wall of stone rose, intercepting the tendrils, but the force shook his massive frame, his brows furrowing in strain.
Obanai darted forward, his movements fluid and unpredictable. "Serpent Breathing – Sixth Form: Coil of the Pale Serpent!" he shouted, his blade dancing around Muzan's defenses.
But Muzan grabbed Kaburamaru mid-air, hurling Obanai into a wall with a sickening crunch. Blood splattered, and Obanai's face twisted in pain, but he staggered to his feet, his eyes blazing with defiance.
Shinjuro roared, his scars glowing with sweat. "Flame Breathing – Fifth Form: Flame Tiger!" A flaming beast tore across the battlefield, its jaws wide.
Muzan countered with a shriek of blood energy, disintegrating the flames, but Sakonji struck from the side. "Water Breathing – Tenth Form: Constant Flux!"
His blade became a spiraling dragon, pushing Muzan back. His face was calm, his movements flawless, but a bead of sweat betrayed the effort.
Muzan hissed, half his face melting from the hit, only to regenerate instantly. "Enough," he snarled, his voice low and deadly.
"Blood Demon Art – Cell Collapse Tempest!"
His flesh exploded into spinning limbs, each sprouting mouths and eyes, a hurricane of death. The battlefield turned crimson, the air screaming with his malice.
Obanai dodged with serpent-like reflexes, his face pale but determined. Gyomei leapt into the fray, his flail leveling entire sections of the castle, his lips still moving in prayer.
Shinjuro's flames burned hotter, his sword a beacon in the chaos. Sakonji moved like the sea, his strikes endless and methodical. But Muzan was unstoppable. He pierced Gyomei's side, sending the giant reeling as he was the strongest of them all. Shinjuro lost two fingers, his face twisting in pain. Obanai's leftwrites, his arm numb, staggered back. Sakonji's mask cracked, blood dripping from his chin.
The original Muzan was poisoned, but now he is at his peak, making it almost impossible for anyone to stop him without sacrifices.
Muzan laughed, his voice cold and mocking. "You struggle for nothing." But the Hashira stood tall. Sakonji whispered, his voice steady, "We might not be able to win… but we are here to give the next generation a chance."
Shinjuro's blade ignited. "Flame Breathing – Ninth Form: Purgatory!" he roared, striking with everything he had. Muzan blocked, but Obanai stabbed from behind, his blade glowing with sunlight steel.
Gyomei crushed the ground, launching Muzan into the air with his battered body. "Stone Breathing – Fifth Form: Arhat's Heavenly Smash!"
he bellowed, his flail smashing Muzan's bones. Sakonji walked through the storm, his blade cutting Muzan's chest. Black blood rained.
Muzan screamed, his tendrils exploding in every direction. Shinjuro's left arm was torn open. Gyomei's weapon was knocked away. Obanai took a hit to the chest. Sakonji was hurled through a wall. But before the final blow could land, a crimson light filled the sky.
Tanjiro, Giyu, and Sanemi arrived, their faces fierce with resolve. The old Hashira collapsed, bloodied but smiling. "Now go… and finish what we started," Sakonji whispered, his voice weak but proud.
But before they could take further action a loud voice was heard throughout the castle after a yelling of someone
"American breathing:first form-glock18"
Then a explosion was heard above and as if space was being destroyed.
CRREEEEEAAAAK.
The castle shattered, fractures spreading through the air. Nakime was slain, and the Infinity Castle collapsed, flinging everyone outside.