First of all, let me say that this is the next part of the future arc of Demon Slayer. This is not a real Demon Slayer. This is just a fan novel. So enjoy it.
The iron stench of rusted bars clung to the air, mixing with the dampness of mildew and sweat. Night had fallen outside the prison walls, but inside, the hours stretched endlessly, measured only by the echoing drips of water and the hollow groans of men who had given up on tomorrow.
Among them sat Kazuya Ubuyashiki, a boy of nineteen, his pale skin bruised and dirtied, his once-proud posture now hunched. His black hair hung in unkempt strands, and his violet eyes—eyes that mirrored the Ubuyashiki lineage—were dulled by despair.
"I didn't do it…" His voice was hoarse, a whisper barely strong enough to reach the cracked stone wall.
But no one cared. To the world outside, Kazuya was already a criminal—labeled a predator, a vile offender.
The accusation had come swiftly, like a blade in the dark. A girl from his village—someone he had spoken with once, someone whose family held power—had accused him of forcing himself upon her. The word spread like wildfire, and though no proof was found, no testimony in his favor was heard, the court still sealed his fate.
"Ubuyashiki Kazuya—guilty."
The irony carved into his heart deeper than any knife. The Ubuyashiki family, who for centuries bore the curse of frailty while leading the Demon Slayer Corps… reduced now, in this era, to a mere name in dusty records. And yet, the same blood that once fought against Muzan Kibutsuji now condemned him without hesitation.
Perhaps it was the curse of his bloodline, Kazuya thought. The same curse that had taken his ancestors young, that had burdened them with frailty, now twisted his fate into something crueler.
Days turned to weeks. He awaited trial, then sentencing. His world shrank to stone, chains, and silence.
Until that night.
The prison guards had drunk themselves into a stupor. The smell of sake hung heavy in the corridor. As they argued drunkenly, one staggered too close to Kazuya's cell. In a moment of desperate clarity, Kazuya lunged forward, seizing the man's keys. His wrists bled as he forced the lock open, scraping skin and tearing flesh, but the door gave way with a shuddering creak.
The drunken guards never woke. By the time the alarm was raised, Kazuya was already sprinting through the forest, his bare feet slapping against mud and moss. Branches clawed at his skin, stones tore at his soles, but freedom burned in his chest.
Three days. Three nights. Hunger gnawed at his stomach, thirst parched his throat, and fever blurred his vision. But still he ran, until the forest thickened, darkened, and a structure emerged from the shadows.
An old, decayed house—its roof half-collapsed, its walls strangled by vines. Windows shattered like jagged teeth grinned at him. The place smelled of death and dust, untouched by man for decades.
Kazuya stumbled inside, his body trembling. He sought water, shelter, anything. But what he found was… wrong.
At the center of the room stood a shattered rack of test tubes, glass scattered like crystals across the floor. Most were dry, but one container—tall, ancient, its glass blackened by age—remained intact.
And inside it sloshed a liquid that pulsed like blood.
Crimson. Thick. Alive.
It seemed to call to him, whispering in a voice that wasn't sound but sensation. A voice older than history, darker than night.
Kazuya's throat ached with thirst. His mind clouded. It's water, he told himself. It has to be. Anything. Just one sip.
His trembling hands pried open the stopper.
The stench hit him first—copper, iron, something foul and sweet. His body screamed against it, but his hunger, his despair, drowned out reason.
He drank.
The world convulsed. His veins ignited as though molten lead was poured through them. His skin split and mended, his bones cracked and reformed. He fell to the ground, thrashing, his screams echoing through the rotting house.
It should have killed him. Any other man would have melted into nothingness, their body unable to contain such venom.
But Kazuya was not like any other man.
The blood of Muzan Kibutsuji—fragmented, preserved, forgotten—flowed into him. And within him, the hidden truth of his lineage stirred.
For generations, the Ubuyashiki family had been cursed. Their lives cut short, their bodies frail, their days numbered. But the curse had roots. Muzan's bloodline and theirs were entwined, tangled since the very beginning.
And so, where another would have perished, Kazuya endured.
The convulsions slowed. His breathing steadied. His vision sharpened, and in the cracked mirror across the room, he saw his reflection.
His once violet eyes now burned with a scarlet glow. His canines lengthened into fangs. His body thrummed with a power both intoxicating and terrifying.
"…What… am I?" he whispered.
The answer came in silence.
He was both man and demon. The curse and its heir.
And in the shadows of that ruined house, the future trembled.
The pale fingers of dawn crept quietly through the narrow slits of the wooden shutter, spilling fragmented shafts of light across the tatami mats where Sumihiko Kamado lay half-conscious. His breathing was slow and uneven, restrained like the fragile flame of a candle flickering in the wind.
The world outside the modest Kamado household was just beginning to stir—a faint chorus of birdsong weaving with the soft rustle of wind over distant trees. Yet inside, the quiet was broken only by a gentle knock and a well-worn voice.
"Sumihiko. It's time to wake up."
Kanata Kamado, his older brother, stood in the doorway with the calm authority born from years of shared hardships and protective care. His eyes, ageless and steady, regarded Sumihiko not as a child but as a bearer of a legacy heavier than either could comprehend.
Slowly, Sumihiko's eyelids flickered, struggling to part as the warmth of family nudged him from the shadows of sleep. His fingers twitched involuntarily, brushing against the faint scar beneath his hairline—a mark that no passage of time had erased.
"You're going to be late if you don't hurry," Kanata said, voice soft but firm. "It's the first day."
Sumihiko sighed, the weight of expectation settling upon his chest, mixing uneasily with the fragile hope that still clung beneath his skin. He rose slowly, allowing the heaviness of dawn to fill him with reluctant resolve.
The air outside the wooden door smelled of morning dew and the distant promise of renewal. Kanata led the way with a steady gait born from years navigating a world forever changed by battles long past, yet whose wounds still ached beneath the surface.
The town's streets were already alive with the murmurs of early morning. Vendors busied themselves arranging fresh produce beneath colorful awnings, the scent of grilled fish drifting lazily through the air. Paper lanterns swayed gently in a breeze scented with cherry blossoms, their soft rustling harmonizing with the distant chime of temple bells.
Sumihiko's footsteps fell softly on the stone pavement, beside him Kanata's steady stride a quiet reassurance against the swelling tide of memories in his mind. His eyes wandered—taking in the familiar yet strange serenity of a town that had long since moved past the shadows of war, yet refused to forget its scars.
As they approached the school gate, a vibrant gust of energy surged forward, cutting through the hum of the morning like a flash of flame. The unmistakable figure of Kyojuro Rengoku bounded into view, hair a blazing crown that seemed to kindle the very air around him.
"Sumihiko! Don't dawdle!" Rengoku called, his grin wide and inviting. "You don't want to start your first day on the back foot!"
Sumihiko returned the smile, the warmth of friendship stirring deep beneath his cautious exterior. Together, the two dashed forward, the ground thundering beneath their feet in a lively rhythm that echoed their shared bloodline of strength and hope.
Kanata's smile lingered at the edge of the gate as he watched his younger brother run alongside Rengoku, pride and concern mingling in his gaze. "Be careful, Sumihiko," he murmured, a quiet prayer threading through his words.
The school itself was a bright, sprawling contrast to the rustic town—clean lines and modern glass windows capturing the sunlight like shining beacons. Students crowded the hallways, a blur of animated voices and laughing faces. To an outsider, it was nothing but an ordinary day—a routine return to lessons and friendships.
Yet beneath the surface, beneath the clatter of footsteps and casual jokes, lay the silent weight of history and promise. Every face carried a legacy etched in blood and courage, every laugh tempered by the remembrance of battles fought and lives lost.
Sumihiko's gaze swept the corridor, landing on familiar figures:
Kurenitsu Agatsuma, curled shyly against a locker, his eyes gleaming with quiet determination.
Aya Agatsuma, whose fiery spirit set her apart, her fists clenched at her sides as if ready for any threat.
Tsubaki Shinazugawa, the tempest incarnate, storming down the hall with a scowl that dared to cross her path.
Kaede Himejima, the calm center of the storm, offered a protective smile to those who sought refuge.
Renji Fujimoto, the steady heart and friend to all, his presence as a quiet anchor in the bustling sea.
And there, always on the periphery, was Kazuya Ubuyashiki—a figure wrapped in shadow and whispers, his crimson eyes betraying a secret darkness reluctant to reveal itself.
The morning sun poured through broad windows, spilling pools of warm light across the wooden floor and into the vast halls of Koyo High School. The scent of polished wood and youthful anticipation mingled in the air, carrying whispers of history and hope.
Sumihiko Kamado found himself swept into the thrumming pulse of school life—a world both ordinary and extraordinary, where the pulse of legendary bloodlines beat quietly beneath the surface.
He glanced around the room, his gaze settling first on Kurenitsu Agatsuma, a tall and calm young man standing near the window. His dark hair fell in neat waves, and his eyes held a quiet strength honed from years of discipline. As the older brother of Aya Agatsuma, Kurenitsu carried the weight of pride and protection like armor around his heart. A hint of thunder simmered behind his steady exterior, a quiet promise that danger would be met with unyielding resolve.
Nearby, Aya Agatsuma leaned against her desk, hair wild and untamed like the storm within her. Fierce and bold, she was a flash of lightning in motion—restless, impulsive, yet deeply loyal. Her fiery gaze softened, just for a moment, as it met Kurenitsu's steady presence.
At the far end, Tsubaki Shinazugawa slammed her palm against her desk, a sharp smirk curling along her lips as she surveyed the classroom. Her wild energy crackled with every breath, a tangible force no one dared underestimate. Descended from the indomitable Sanemi, her spirit stormed like the fiercest winds, bold and relentlessly fierce.
By the library alcove stood Kaede Himejima, tall and serene like a mountain carved from stone and kindness. Her calm eyes observed the room with quiet understanding, straddling the line between protector and confidante. The legacy of Gyomei's gentle strength dwelled within her, a bastion amid chaos.
And then, with subtle footsteps and guarded glances, came Renji Fujimoto. Though lacking the bloodline of a Demon Slayer, Renji had earned his place through unwavering loyalty and unshakable courage. His presence, steady as an anchor, brought balance to the group's swirling energies.
Sumihiko's eyes found the enigmatic figure hovering near the shadowed doorway—Kazuya Ubuyashiki. His crimson eyes flickered faintly like distant embers beneath a calm yet unreadable expression. Whispers of Muzan's cursed blood swirled like dark smoke around him, sending a chill through the room despite his distant silence. An heir burdened by heavy secrets, his every step seemed measured, as if the weight of a thousand battles pressed upon his shoulders.
Voices rose and fell, fragments of conversations weaving a tapestry of tentative friendships and unspoken rivalries. Sumihiko felt the gaze of his peers, some curious, others cautious. Beneath the veneer of casual interaction lay the undeniable truth—they were bound by legacy, by blood and destiny alike.
As the midday bell chimed, the teacher's voice cut through the murmurs, summoning attention. Yet even her words could not mask the uneasy tension settling like a shadow over the room.
They did not yet know what awaited them beyond these walls, what darkness stirred unseen.
Sumihiko Kamado's footsteps echoed lightly in the quiet streets, his breath measured as he walked beside his elder brother, Kanata. The morning was wrapped in soft golden light, and the city was slowly coming to life—vendors setting up stalls, children's laughter spilling over low walls, and the distant ringing of the temple bell marking the hour.
"They say this town has changed so much," Kanata began, voice low. "But beneath it all—the river, the mountains—they remain the same."
Sumihiko nodded, watching a school group burst into laughter not far ahead. "I just hope I can live up to the name Kamado."
Kanata's smile was patient, understanding. "You don't carry a legacy to be a burden. You carry it to be a beacon."
As they approached the gates of Koyo High School, the crowd thickened with students pouring in. The air buzzed with nervous excitement—the chatter of first days and new friendships.
Suddenly, the unmistakable burst of flame-red hair cut through the crowd. Kyojuro Rengoku appeared, his grin blazing brighter than the sun itself.
"Sumihiko! Don't dawdle!"
Grinning back, Sumihiko quickened pace to run alongside the Flame Hashira descendant. Their feet pattered rhythmically against the pavement as they laughed and exchanged hopes for the new day.
Inside, the school felt alive. Classrooms filled steadily as students bargained social power and whispered ancestral tales. The descendants of the Demon Slayer Corps carried their dual burdens quietly—walking the line between ordinary life and fateful legacy.
Sumihiko passed faces woven with recognition: Aya Agatsuma with her restless spark, her older brother Kurenitsu's composed gaze, fierce Tsubaki Shinazugawa's challenging smirk, Kaede Himejima's quiet strength, and Renji Fujimoto's warm steadfastness.
Yet, beneath the laughter, an unknown tension hummed—not palpable, but there.
No one noticed the faint rustling in the school yard's overgrown bushes. Nor the chill that snaked its way through the hallways. No cautious word, no whispered warning.
Until—
Crash.
The world exploded.
Windows shattered with violent force, showering shards through the corridor and striking the floor like deadly rain.
Students screamed and scrambled, eyes wide as terror crashed upon them like a wave.
From the broken window, a dark shape lunged—a demon, more nightmare than flesh, its twisted form contorted and leaking shadow. It moved with unnatural speed, claws tearing through desks, its eyes blazing with ancient hunger.
Chaos tore through the room.
Tsubaki lunged forward, fist striking carved stone. "Get out of the way!"
Aya's voice cracked sharp, sweeping students calling, "Move! Get to safety!"
Kurenitsu roared commands, rallying the frightened crowd. "Stay close together!"
Sumihiko froze, heart hammering. Then, Kazuya Ubuyashiki stepped from the shadows—his red eyes burning in the chaos, claws slicing the darkness as he tore into the demon's flesh.
The battle raged—a tangle of screams and fury, fear and desperation.
Sumihiko met the eyes of friends and strangers alike—faces shocked, hearts pounding. The weight of legacy flamed anew inside him.
A light, hazy body that looked a lot like Sumihiko, placed a hand on Sumihikor's shoulder.
"You can do it boy," Kamado Tanjiro whispered in his ear, blade singing arcs of fire.
Trapped between terror and resolve, Sumihiko's hands clenched, and the fight for tomorrow began.