Reborn as Tanjiro with a System

The first light of dawn barely touched the sky when Tanjiro stirred from his sleep. The cool mountain air wrapped itself around him like a familiar embrace as he slowly opened his eyes. His breath created faint clouds in the air, and the silence of the early morning was broken only by the soft rustling of leaves outside.

Tanjiro Kamado, at just twelve years old, was already hardened by the demands of mountain life. His height, though not particularly remarkable at 150 centimeters, was packed with a quiet strength earned through years of work for his family. His long, dark hair fell loosely down his back, and his face bore a distinct marking—a flame-like crest on his forehead, a mark that, while curious to some, felt to him as if it had always belonged. His features were sharp yet soft at the same time—his eyes warm, compassionate, like a calm stream yet holding the intensity of a fire waiting to be kindled. It was an odd mixture: the solemnity in his gaze paired with the kindness his mother had nurtured in him since birth.

As he sat up, he reached for his belongings—his shortsword-like dagger strapped tightly to his leg, and his axe, sharp and worn from use, lying by his side. These were the tools of his trade, tools that would provide for his family today just as they had countless times before.

Without wasting time, Tanjiro stood, washed his face in the cold basin, and took one last glance at his sleeping siblings. They were still nestled warmly beneath their blankets, breathing softly in the comfort of their small, humble home. His mother, Kamado Kie, was the last to stir. She smiled at him in the quiet way that mothers do when they recognize the early burden their child carries. Her gaze held pride and concern in equal measure, but there was an unspoken understanding between them. He would be careful, and he would return.

Stepping out of the house, Tanjiro breathed deeply, savoring the fresh mountain air. The tall, looming forest ahead stood waiting for him, dense with trees and thick with shadows. His family's livelihood depended on these woods—both in the wild game that roamed within and the wood he would chop for charcoal. With a glance up the mountain, the boy began his descent toward the forest below.

The forest was alive with activity as dawn turned to morning. The faint sunlight filtered through the thick canopy above, casting dappled shadows onto the ground. His boots crunched on the frost-covered leaves, the sound blending with the gentle calls of birds waking in the trees. His senses, sharpened from years of this routine, quickly caught the scent of nearby game. It was faint, but there—wild boar, likely just ahead.

With a steady hand, Tanjiro drew his shortsword-dagger, feeling its familiar weight. It wasn't a true sword, but he had no need for one. The weapon was more than enough for the tasks at hand. He crouched low, his movements quiet, fluid, as if he were one with the forest itself. His demeanor, calm and focused, not unlike a professional Hunter a master of killing. Tanjiro had been taught this way by his Father from early on. While he seemed cold and murderous form outside, there was something softer about the boy—an undercurrent of gentleness that never left his expression, even as he prepared to hunt his prey.

Moments later, Tanjiro spotted the boars. They were large and bristling, snuffling at the ground for roots. He waited, his eyes narrowing as he judged the distance. Then, in a swift and decisive movement, he struck. The blade met flesh with a quickness and precision that spoke to years of practice, and within moments, the boars were down. They would provide plenty of meat for his family.

But Tanjiro's work wasn't finished. He still needed wood. He found a clearing not far from where the boars had fallen and set to work with his axe. The rhythmic sound of chopping echoed through the forest, each swing purposeful and efficient. His arms moved with ease despite the weight of the axe, and the tree soon fell. As he chopped the logs into smaller pieces, he stacked enough to last his family through the week—a task he had long mastered.

The sun was high in the sky by the time he finished, and with the game tied to a makeshift sled and wood strapped to his back, Tanjiro made his way back home. The return journey was more strenuous with the added weight, but his steps were sure, and his mind was filled with thoughts of his family.

As he reached the familiar threshold of their small, wooden house, the sounds of his siblings laughing and playing greeted him. The door swung open as his oldest sibling, Nezuko, came running out, her feet pattering against the earth as she called out his name. Behind her, his other brothers and sisters followed, their faces lighting up as they saw the fruits of his labor.

"Tanjiro! You're back!" Nezuko grinned, her bright eyes full of joy.

He smiled, his heart swelling with the warmth of his family's love. His mother, Kie, appeared in the doorway, her face soft with pride. She welcomed him inside, and soon the family was gathered around, enjoying a hearty meal of boar meat roasted over the fire. The room was filled with laughter as they recounted the day's small triumphs and shared stories.

Later, as the evening settled in and his siblings prepared for bed, Tanjiro sat with his mother by the hearth. The fire crackled softly, casting flickering shadows across the room.

"Mother," Tanjiro began, his voice thoughtful. "I've been thinking about the dance... the one father used to perform. You've told me about it before, but I feel like there's more to it than just a tribute to the gods."

Kamado Kie's eyes softened. "Ah, the Dance of the Fire God," she said quietly. "Yes, there's much more to it than simply honoring the gods. Each movement, each stance, carries meaning. It's a dance that has been passed down for generations, and it's more than just tradition. It's a prayer, a connection to something greater."

Tanjiro listened carefully, his mother's words sinking into his heart as she explained each stance, each breath. He had always performed the dance out of respect, but now he was beginning to understand that it was more than just a ceremony. It was a way of life, a way to offer something of himself to the divine.

As the night wore on, the fire dimmed, and Tanjiro knew it was time to descend to the village below. The charcoal he had prepared would fetch them enough money to get by for another week. With a final goodbye to his mother and siblings, he began the walk down the mountain, the familiar path winding through the forest and eventually leading to the village at its base.

The people of the village greeted Tanjiro warmly. He had always been a friendly face among them, his kind nature making him well-liked by the townsfolk. He spent the afternoon chatting with the villagers as he sold his charcoal, enjoying the sense of community that came with each interaction.

As dusk began to settle, one of the elders of the village, Saburo, called him over.

"Tanjiro, you should stay the night here," the old man warned, his voice low and serious. "There are demons in these woods. You don't want to be out after dark."

Tanjiro smiled politely, though his brow furrowed slightly. "Demons, you say? I've never seen one."

"That doesn't mean they aren't there," Saburo said, his tone grave. "It's not safe to take that chance."

Tanjiro, though still dubious, respected the elder's caution. "I'll be careful, Saburo-san," he promised.

The elder nodded but didn't look convinced. As Tanjiro made his way back up the mountain, the sky growing darker with each passing minute, a strange feeling crept over him. The wind felt colder than usual, and the forest, once so familiar and welcoming, now seemed almost... watchful.

He shook off the feeling, reminding himself of Saburo's warning. Still, as he climbed, he couldn't help but feel that something had shifted. Something, though unseen, had taken root in the world around him. He carried on, unaware that a subtle change had already begun within him, set in motion by forces far beyond his understanding.

And as the stars blinked into the darkened sky, Tanjiro Kamado continued his journey, blissfully unaware of the destiny that had already begun to unfold.

Muzan Kibutsuji sat in the heart of a lavish mansion, veiled by shadows despite the flickering candles around him. His cold, pale hand tapped rhythmically on the armrest of his ornate chair. The silence of the room was thick, save for the occasional rustle of his black silk robe. His crimson eyes stared ahead, unblinking, their depth betraying the centuries he had lived and ruled from the shadows. He was the Demon King, the progenitor of all demons, and for over a thousand years, his goal had been singular—immortality under the sun.

Yet, despite all his power, Muzan's greatest fear haunted him still: Sun Breathing. The cursed technique wielded by Yoriichi Tsugikuni centuries ago had nearly ended him, and the thought of someone reviving that threat sent a wave of icy rage through his veins.

As he sat, an unsettling presence slithered into the room—a lower-ranked demon, crawling on all fours, trembling as it approached its master. Muzan's gaze did not shift, but the air grew heavy with the demon's fear.

"Speak," Muzan's voice was soft but absolute. There was no need to raise his voice; the power within his words alone crushed those who disobeyed.

The demon quivered, its voice barely a whisper. "M-my lord, there are rumors… whispers from the mountains... about a family living near the summit. There's talk of a boy who… who might practice the dance… the Sun Dance."

For a moment, Muzan remained silent, his expression unchanged. But internally, a wave of fury surged through him. He could not tolerate the existence of even a trace of Sun Breathing. The demon at his feet, sensing Muzan's displeasure, recoiled further, bowing low.

"A family?" Muzan finally asked, his voice cold and deliberate.

"Y-yes, my lord. The Kamado family. They live in isolation, but the boy—the eldest son, Tanjiro—he performs a dance, they say… a ritual passed down for generations."

Muzan's fingers tightened on the armrest, the wood groaning under the pressure. "A dance…"

A mere dance couldn't be ignored, especially one rumored to be connected to Sun Breathing. Yoriichi had been unmatched in his mastery of that cursed technique. If someone was attempting to recreate it, they would need to be eradicated, no matter how small the threat seemed.

Muzan stood, his decision made, and he'd do it inconspicuously. "Prepare my horse. I will deal with this personally."

The demon didn't dare look up but bowed repeatedly as it scurried away. Muzan moved toward the window, gazing out at the moonlit sky, the light casting eerie shadows on his features. This family, these whispers—they would not survive the night.

Meanwhile, high on the mountain, the Kamado family home was filled with warmth and light. Tanjiro had returned from the village, the day's earnings tucked safely into his bag. He stepped into the modest house, the crackling of the hearth fire and the sound of his siblings' laughter welcoming him home.

"Tanjiro!" Nezuko cried, running over to hug him. She held on to him tightly, her eyes shining with excitement. "How did it go in the village?"

Tanjiro smiled, his heart swelling with affection. "It went well, Nezuko. The charcoal sold quickly today."

He handed the money to his mother, Kamado Kie, who smiled warmly at him, her face full of quiet pride. "Thank you, Tanjiro. You always work so hard for us."

They gathered around the table to share another meal of the boar Tanjiro had hunted earlier. The meat was rich and filling, and the children giggled and chatted as they ate, their voices blending with the sound of the crackling fire. The atmosphere was one of peace and contentment, a simple moment of family togetherness.

As the night wore on, the younger children began to tire. Kamado Kie gently guided them to their futons, tucking each one in with a loving hand. Soon, the house fell into a peaceful silence, the quiet breathing of his siblings filling the room as they drifted into slumber.

Tanjiro sat near the door, breathing in deeply. He felt something—an odd sense of relief, yet confusion, as if he was in a dream. But this wasn't Tanjiro anymore. Not truly.

When he had climbed the mountain earlier, something had changed. A fluid exchange had taken place—a soul for a soul. The new soul within Tanjiro's body now sifted through his memories, absorbing them with a strange detachment. He saw all that Tanjiro had lived, the love for his family, his strength, his resolve. This boy was good—too good for this world.

The new soul blinked, momentarily distracted by a floating window that appeared before his eyes. It was strange, otherworldly, visible only to him.

"System Activated: Swordsmanship-Style Database."

The soul frowned slightly. What is this? He focused, and the window expanded, explaining its function. It was a system designed to provide various styles of swordsmanship, tested and refined by the greatest masters across time and space. Each style would be imparted to the user based on their compatibility, and the mastery of these styles could be improved over time.

A list materialized:

Musashi Style (35% mastery)William Marshal Style (41% mastery)Mihawk's Swordsmanship (98% mastery, including Haki)Sun Breathing (full access, attunement granted due to the Dance of the Fire God and the mark)

A low chime echoed in his mind as these styles began to integrate into his body. The sensation was strange, but exhilarating. Musashi's dual-sword techniques felt complex, but natural. William's knightly prowess gave him an understanding of battlefield tactics and shield use, despite him having no shield. But Mihawk—his near-perfect mastery—gave him the confidence of a swordsman who had fought a thousand battles. With it came the sudden awareness of Haki: the ability to dominate the will, to harden his body beyond normal limits. He felt power surging through him, but there was also an understanding that Haki would protect him from the sinister effects of demons.

When the integration was complete, he exhaled. He felt sharper, stronger, as though he had lived and trained for decades in a matter of moments. His senses were heightened, and the world seemed clearer—perhaps a side effect of the Transparent World, a gift he hadn't fully realized until now.

So, this is my new reality, huh? The soul mused. I guess I'm Tanjiro now… It's strange, knowing the future from that story…

He paused, his thoughts trailing off as a knot of dread tightened in his chest. Muzan… He's coming tonight.

The memory of the series flooded back. He remembered this night vividly—the night Muzan Kibutsuji would slaughter Tanjiro's family. Panic surged, but he forced himself to remain calm. He had time, and now he had power. I can change this.

Just as he thought this, a soft knock echoed through the house.

Tanjiro stiffened, his heart pounding. Without hesitation, he strapped his shortsword to his leg and moved silently to the door, his hand poised on the handle. He opened it cautiously, only to be met with a chilling presence.

Standing in the doorway was none other than Muzan Kibutsuji. His pale skin gleamed under the moonlight, and his crimson eyes locked onto Tanjiro's. For a brief moment, Muzan's face was expressionless—then his gaze shifted to Tanjiro's hanafuda earrings, and rage sparked within him.

Without a word, Muzan lunged forward, his fingers extending into deadly claws. But Tanjiro had seen this attack coming through the Transparent World. He sidestepped effortlessly, the new instincts and mastery of Mihawk's techniques guiding his body as he made distance between them.

The house behind them groaned and collapsed, the weight of the demon's attack crushing it instantly. Tanjiro's family—his mother, his siblings—were caught beneath the rubble. He knew what had happened, but there was no time to grieve. If he hesitated, he would die too.

Muzan's form shifted grotesquely, his demonic presence growing more monstrous. But Tanjiro, now fully in sync with the new skills flowing through him, engaged without fear. His blade clashed against Muzan's claws, and the sound of steel meeting flesh filled the night.

Using Mihawk's near-perfect swordsmanship, Tanjiro pressed Muzan into a corner, his blade glowing with the power of Haki. Each strike was precise, fueled by the adrenaline of battle and the overwhelming need to protect what little remained of his world.

But just as he prepared to deliver a decisive blow, Muzan vanished, disappearing into the night with only a faint trail of blood left behind. The distant sound of a biwa being played echoed faintly through the mountains.

Tanjiro stood alone, panting, his sword still raised. The battle was over, and he had survived. But the cost… His family. His home.

A calm, dangerous anger began to settle in his heart. The kind of anger that did not rage, but promised quiet, unwavering vengeance. He had failed tonight, but this wasn't over.

Not by a long shot.

Tanjiro Kamado knelt in silence before five freshly filled graves, their mounds of earth meticulously shaped, and a sense of finality clung to the air like a heavy shroud. The graves were marked not by ornate headstones, but by a single stone tablet—crudely scratched with a message that carried the weight of a boy's shattered heart. Around the graves, in a tender oval pattern, lay clusters of wildflowers, their bright colors standing in stark contrast to the grim scene, as if nature itself sought to soften the brutality of death.

The stone bore words etched by Tanjiro's own trembling hands:

Here rest the Kamado family. My mother, my brothers, and my sisters—taken from this world by the King of Demons.

To anyone who reads this, beware: demons are real. They lurk in the shadows. Protect your loved ones. Take care. —Tanjiro Kamado

Tanjiro's fingers dug into the dirt beneath him, but his expression remained calm, stoic. He had no tears left, not after the sleepless nights spent burying them, digging the graves with his bare hands and carving their story into the stone. The pain was deep, not just physical, but the kind that gnawed at his soul. His family, gone, and he had failed to protect them.

He felt like Yoriichi Tsugikuni—the legendary swordsman whose power had once shaken Muzan to his core—yet who had also failed to rid the world of demons. Tanjiro could feel the same failure settling like a stone in his heart. The body that housed him now remembered the warmth of family, the love of a mother and siblings. It was a warmth he had barely known in his past life. To experience it for even a short time, only to lose it all again… it was a wound that cut deeper than any blade.

The wind stirred gently, carrying with it the distant sound of rustling leaves. Tanjiro looked out at the mountain, the home he had known reduced to nothing more than a memory. The weight of his mission, the promise of revenge, pressed down on him. I won't fail again.

Elsewhere, Tomioka Giyuu moved silently through the forest, his long black hair flowing behind him like a shadow. His expression was as cold and stern as ever, his blue haori swaying with the rhythm of his steps. As a member of the Demon Slayer Corps, his job was clear—hunt demons, protect humanity. But today, something was different. His crow, Kanzaburo, had led him to the mountain where the Kamado family resided, a place now marred by tragedy.

Tomioka's sharp eyes scanned the scene from a distance, but it wasn't the graves or the flowers that held his attention. It was the boy sitting before them—just a child, no older than 12 or 14, with long reddish-black hair that cascaded down his back. The boy's posture was rigid, unmoving, and for a moment, Giyuu was reminded of himself.

As Giyuu approached, his eyes caught sight of the message on the stone tablet. His breath hitched, a rare moment of surprise crossing his usually emotionless face.

Demons are real. The King of Demons… Muzan Kibutsuji.

The mention of Muzan, the progenitor of all demons, left no doubt in his mind—this boy had encountered something monstrous. Giyuu raised his arm and called for his crow. "Kanzaburo, relay this message to Ubuyashiki-sama. Inform him of the boy's words. I will investigate further."

With a flap of wings, the crow disappeared into the sky, carrying the weight of this new revelation to the Demon Slayer Corps' master. Giyuu approached the boy, his footsteps barely audible on the forest floor.

"You fought him," Giyuu said quietly, standing just a few paces behind Tanjiro.

Tanjiro looked up, his eyes dark and hollow but still burning with quiet resolve. "Yes," he said, his voice steady. "Muzan Kibutsuji… he killed my family. I couldn't stop him."

There was no hesitation in Tanjiro's voice, no bravado—just the simple, bitter truth. Giyuu knelt down beside him, studying the boy's face. There was something about him that struck a chord deep within the usually distant swordsman. He saw a reflection of himself in the boy's quiet grief, in the way Tanjiro carried the weight of his failure.

"You're not alone," Giyuu said after a long pause. "I understand what it's like to lose everything to demons. That's why I fight. It's why you should fight too."

Tanjiro turned to him, the ghost of a question forming in his eyes.

"I want to teach you," Giyuu continued, his tone firm. "To become a Demon Slayer. To protect yourself and others. Alone, you'll only die. But with the Corps, you can find strength, purpose. It's your choice."

The offer hung in the air, heavy with promise. Tanjiro didn't need long to consider it. He had already made up his mind the moment he buried his family. He couldn't live on his own, and he couldn't bear the thought of leaving others vulnerable to demons like Muzan. He wanted to fight—not just for revenge, but for something greater.

"I'll do it," Tanjiro said, his voice unwavering. "I'll become a Demon Slayer."

Their journey was swift. Tomioka moved quickly, leading Tanjiro down the mountain paths, across rivers, and through forests until they reached a secluded area where a humble residence stood, nestled against the mountains. As they arrived, Tanjiro noticed the presence of others—powerful presences. Several people stood around, their eyes sharp and curious.

Waiting for them was Sakonji Urokodaki, Tomioka's mentor and the former Water Pillar. The old man's face was hidden behind his signature tengu mask, but there was an air of authority in his stance. Beside him stood Kagaya Ubuyashiki, the master of the Demon Slayer Corps, flanked by his wife, Amane. Their expressions were soft, kind, yet their eyes gleamed with a deeper understanding.

The other Pillars—the elite of the Demon Slayer Corps—were there too. Each one exuded a different kind of strength. There was Kyojuro Rengoku, the Flame Pillar, with his fiery spirit and unwavering smile. Sanemi Shinazugawa, the Wind Pillar, with a fierce, volatile energy barely contained beneath his scarred skin. Mitsuri Kanroji, the Love Pillar, stood with her gentle warmth, while Gyomei Himejima, the Stone Pillar, loomed like a silent mountain.

Tomioka stepped forward, introducing Tanjiro to the group.

"This is Tanjiro Kamado," Giyuu said. "He fought Muzan Kibutsuji and survived."

The words hung in the air like a challenge. Several of the Pillars exchanged glances, intrigued but skeptical. To face Muzan and live was unheard of. Tanjiro, though younger and smaller than any of them, stood firm, meeting each of their gazes without faltering.

After the introductions, Tanjiro gave a brief recount of his encounter with Muzan—how his family had been slaughtered, how he had barely managed to escape. But his story didn't end there.

"I'll bring him down," Tanjiro said, his voice filled with a quiet but deadly resolve. "I don't care how long it takes. I'll defeat the King of Demons."

This proclamation stirred something within the Pillars. A challenge had been laid before them, and despite their differences, they shared one common goal: to kill Muzan. Rengoku's grin widened, and Sanemi let out a low chuckle. A sense of rivalry sparked in the air—friendly, but intense.

"If it's a race to defeat Muzan, count me in," Rengoku said, fire blazing in his eyes.

"We'll see who takes him down first," Sanemi added, his voice rough but not unkind.

As the Pillars acknowledged Tanjiro's resolve, the boy opened up more. He shared his knowledge of demon locations and missions from the series he had known in his previous life. Though vague, his insights were enough to make the Pillars listen closely.

But it wasn't just information that he brought. He spoke of techniques—the marks, the Transparent World, and the risks that came with mastering them.

"It's dangerous," Tanjiro warned. "The more you push your body, the higher the risk of dying. But if we want to defeat Muzan…"

"We'll do whatever it takes," Gyomei rumbled, his deep voice resonating through the room. "The cost is irrelevant if it means saving humanity."

The meeting concluded with the understanding that they would need to prepare, to train harder than ever before. And Tanjiro, now standing among them, knew his journey was just beginning. He would train under Giyuu and the other masters of the fundamental styles, honing his swordsmanship and learning all he could.

'The next time I meet you, Muzan, YOU WILL FALL!!!'