The Zenin estate at night was a place of whispers.
Wind sighed through tall bamboo and the gravel paths glittered with moonlight. Somewhere deeper in the compound, blades clashed faintly—guards or disciples finishing their drills. But here, near the unused training yard behind the east wing, the world felt still.
A small figure stood in the center of that courtyard, the shadow of a boy no older than five.
His name was Koujin Zenin.
The wooden practice sword in his hands was longer than his arm span. Each swing looked clumsy at first—shoulders too tight, stance too narrow—but he kept going, breath after breath.
"Sixty-two… sixty-three…" he murmured, counting softly. His voice barely rose above the rustle of bamboo.
By the time he reached eighty, his arms burned and his palms were raw. He could have stopped, but the thought of stopping made something inside him twist.
He wasn't supposed to exist, not in this clan.
Koujin had learned early that the Zenin family smiled only for strength.
When he was three, one of the elders had placed his tiny hands against a charm stone used to test cursed energy. It stayed dim. The room grew quiet. Someone sighed.
That was the day he learned what "failure" sounded like.
Since then, the servants whispered around him. Some pitied him, others simply forgot he was there. The only people who ever treated him like a person were his sisters, Maki and Mai, though even they were often away training—or fighting each other.
Maki always told him, "You don't need cursed energy to fight."
But the way the clan treated her for it… he understood that her path was carved in blood.
Koujin, smaller and quieter, had no choice but to find his own way.
Sometimes he dreamed of a different sky.
In that other life, he was Dante Ishikawa, a second-year high-school student who stayed up too late watching anime. He remembered sitting in his room, watching Demon Slayer on an old laptop, thinking how beautiful the breathing techniques looked—how the swordsmen seemed to dance with death.
He remembered the last night of that life too: earbuds in, a crosswalk light flashing red, a sudden glare of headlights.
After that, nothing.
Then warmth. Crying. Voices speaking names he didn't know.
He had been reborn—no, transferred—into a world he used to watch on a screen. A world where curses were real, where people like Gojo Satoru existed.
At first it was exciting.
Then it became terrifying.
Because even here, even in a world full of power, he was still ordinary.
He adjusted his stance and swung again. The wooden blade sliced through the air with a sharp whff.
"One hundred," he gasped. He lowered the sword and fell back onto the grass.
His breath steamed in the cold. The moon above him was thin and bright, shaped like a silver crescent. He stared at it for a long time, chest rising and falling.
"…Still weak," he muttered.
The word didn't sting anymore. It was simply the truth.
He lay there, watching the clouds drift past the moon, and whispered, "Kokushibo would've hated someone like me."
The name slipped out without thinking. Kokushibo—the terrifying swordsman with six eyes, the one who sought perfection even after death.
Dante used to think he was tragic. Now Koujin saw something else in him: determination so sharp it cut everything around it.
He rolled to his feet again, refusing to rest. "If cursed energy won't answer me, maybe the moon will."
He raised the wooden sword once more. This time he tried something different. He inhaled deeply through his nose, expanding his chest, and exhaled slowly through his mouth—the rhythm he remembered from those anime scenes.
Breathe in. Hold. Breathe out.
The world sharpened. Every sound grew clearer: the sway of bamboo, the crackle of a torch somewhere nearby, even the distant drip of water from a roof gutter.
He swung.
The air shimmered. For the briefest heartbeat, a pale line of silver followed the wooden blade before fading.
He froze.
"…That wasn't my imagination."
The ground beneath him seemed to hum. A faint vibration ran up through his legs into his chest. Then—light.
Soft, translucent light filled his vision, forming words that floated in the air.
[System Initialization Detected]
System Type: Bloodline / Combat Template
Template Reference: Kokushibo
Status: Awakening… Complete.
Koujin blinked hard. "W-wait—what?"
He rubbed his eyes, but the glowing text stayed.
You are not becoming Kokushibo.
You are inheriting his path.
His heart pounded. "A… system?"
He'd read so many WebNovels with lines just like that. But this was Jujutsu Kaisen's world—systems didn't just appear here. Yet the light in front of him pulsed, waiting.
New lines appeared.
Stage 1 – Crescent Initiate (Active)
• Perception +30 %
• Enhanced night vision
• Pain resistance
• Accelerated muscle learning
Breathing Style Access: Moon Breathing (Incomplete) – Forms 1–3
Notice: Technique stability improves with practice.
Koujin's mouth went dry.
"Moon Breathing… like in Demon Slayer?"
He reached out instinctively, trying to touch the text. His fingers passed through light and nothing. The interface shimmered, then condensed into a faint silver sigil on the back of his hand—half a crescent, glowing softly.
His whole body trembled. "This is real."
The night air felt different now—thicker, alive. He could feel each heartbeat, each pulse of blood in his veins.
He lifted the sword again.
Inhale… hold… exhale.
The world slowed. He moved.
A flash of silver carved the darkness.
The crescent vanished a moment later, but the shock of it rattled through his bones.
[Skill: Moon Breathing – First Form: Dark Crescent (Unstable)]
Pain exploded in his chest. He stumbled, nearly dropping the sword. His small frame wasn't built for this—lungs burning, arms shaking.
He fell to his knees, panting.
"Hurts… but—it worked."
He laughed weakly. The sound echoed through the empty courtyard, half-cough, half-joy.
He sat there until the trembling eased. When he finally looked up again, the moon seemed larger, almost watching him.
[Quest Generated]
Origin Quest – First Reflection
Practice sword forms under the moonlight for 100 consecutive nights.
Reward: Stabilize Moon Breathing Form 1.
Failure: Progress resets.
"One hundred nights…" he whispered, reading the floating text. "That's… a lot."
But the corners of his mouth lifted. "Then I'll start with night one."
He pushed himself to his feet, legs shaking. He bowed slightly toward the moon without knowing why, then limped toward the small house that served as his room.
⸻
Inside the Small Room
His room was little more than a futon, a desk, and a cracked mirror. He placed the wooden sword against the wall and collapsed onto the futon.
Every muscle screamed. His lungs still burned from that single technique.
He stared at the ceiling. "I really got a system…"
A quiet laugh escaped him. The sound was small but full of disbelief.
If he still had his old phone, he'd probably be spamming his group chat about this—Guys, I just unlocked Moon Breathing in JJK, what now?
The thought made him smile before sleep finally dragged him under.
He dreamed of a battlefield covered in ash.
A man with six eyes stood beneath a broken moon, his blade glowing with countless crescents of light.
Each swing tore the sky apart.
When the man turned, Koujin saw his own face reflected in those many eyes.
"Walk the path, child," the voice echoed.
"Perfection is not reached—it is remembered."
Koujin reached for the man, but the vision scattered like glass
⸻
He woke to sunlight slipping through the paper windows. His arms ached. His chest felt heavy.
For a moment he thought it had all been a dream—until he noticed the faint silver mark still glowing on his hand.
"Not a dream," he whispered.
He sat up slowly. Outside, servants were already sweeping the courtyard. Somewhere, Mai's laughter echoed faintly; Maki's sharp tone followed, scolding her about something.
For a second, he imagined telling them what had happened. Then he shook his head. The clan already thought he was strange; this would make things worse.
No—this was his secret for now.
At breakfast, the main hall buzzed with quiet conversation. Dozens of clan members sat in orderly rows. Koujin slipped into a corner seat near the back. Few even noticed him.
Naoya Zenin's voice carried from farther down the table. "Another report of curses near the outskirts. Pathetic sorcerers couldn't even exorcise them properly."
Koujin kept his head low. Naoya never spoke to him directly, but the boy's gaze occasionally swept over him like a knife, filled with disgust.
He forced himself to eat quietly. Every movement felt mechanical.
But inside, his mind replayed the moment from last night—the flash of light, the crescent trail.
It was real. I can do this.
He finished eating, excused himself, and slipped away before anyone could stop him.
⸻
The Second Night
That evening, he returned to the courtyard. The same moon hung above, thinner now. He took his position again, sword in hand.
"Night Two," he whispered.
He breathed in, finding the rhythm. The wind carried the scent of bamboo and dew. He swung once, twice, ten times—each slower, smoother.
[Muscle Memory + 1 %]
[Technique Stability Improved]
The faint notifications flickered at the edge of his vision. He grinned.
"Looks like you really respond to effort," he said softly. "Good."
The silver mark on his hand pulsed faintly in response, as if agreeing.
Hours passed before fatigue finally won. He dropped the sword and looked up at the sky.
The moonlight painted the scars on his palms pale white.
"One hundred nights," he repeated. "Then I'll be strong enough to stand beside them… maybe even against them."
The breeze stirred again, carrying the quiet hum of the system in the back of his mind. It wasn't commanding him; it felt like a silent partner, patient and steady.
For the first time since his birth into this world, Koujin didn't feel trapped by fate.
He felt like he had a direction—one carved in silver light.
⸻
He lay back on the cool grass, exhaustion turning to calm.
Above him, clouds drifted aside, revealing the full curve of the moon.
Somewhere in the shadows, unseen, a faint ripple of cursed energy stirred—something ancient watching from the edges of the Zenin grounds.
But Koujin didn't notice.
He had already closed his eyes, a small smile forming as he whispered:
"Thank you… for answering me."
The crescent mark on his hand glowed once, then faded as he drifted into sleep.
[End of Chapter 1]