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silence is poison~

Summary:

She vanished without a trace — and the Corps whispered her name like a ghost.

Shinobu Kocho, once a prodigy, now lives hidden among humans, crafting poisons capable of killing demons without a blade. A quiet vengeance.
A death wish disguised as purpose.

But when Giyu Tomioka finds her again, everything she buried begins to surface — grief, rage, tenderness she can’t afford. He wants to save her.
A demon wants to keep her.
And Shinobu… isn’t sure she wants either.

As love, loyalty and obsession tighten around her like threads of silk, one truth becomes impossible to ignore:

Not all demons hunger for flesh —
and not every hero longs to live.

Notes:

Hello everyone and welcome to my first fanfic!

What can I say — Shinobu just completely captured my heart from the very first moment I saw her.
This is one of my countless ideas and my way of dealing with her canon story.

English is not my first language, so I want to apologize in advance if I repeat myself sometimes or make small mistakes.
I hope it’s still readable and that you can relax a little while reading this.

Thank you already for taking the time to read it — I appreciate every bit of feedback 💜

Chapter 1: Nightmare-

Chapter Text

1️⃣

 

I've tasted blood and it is sweet
I've had the rug pulled beneath my feet
I've trusted lies and trusted men
Broke down and put myself back together again
Stared in the mirror and punched it to shatters
Collected the pieces and picked out a dagger-
Nightmare by halsey
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It was a calm, clear night.
The moon hung high in the sky, bathing the city in a pale glow that made it seem like an entirely different world. Forgotten were the crowded streets, the cheerful, stressed, and noisy voices, the worries and hopes. Most of the residents were asleep, preparing for the next hours, the next day, or perhaps, unknowingly, the rest of their lives.

How tempting.

For Shinobu, the night had always held a special fascination. Finally, there was silence. Finally, there was time. And above all: finally, there were no questions.

Yet, in all this quiet, one might forget that the night was far from safe. In this world, it wasn’t only the cicadas that awoke after sunset.

A strange tension lingered in the air, sending a shiver down her spine—half unpleasant, half thrilling. With a charming smile, she made her way toward the edge of the city. The few lingering townsfolk cast curious, friendly, or sometimes indecent glances her way.

Fools, she thought. That was all they were.

The farther she walked, the fewer people there were. Less light. Fewer smells. In the distance, the dark outline of the forest finally appeared, letting her breathe freely for the first time.

She checked herself one last time. Had she brought everything for tonight’s plan?

All set.

A bright giggle escaped her lips as adrenaline surged through her veins. Her newest creation waited to be tested, and she hoped for a breakthrough. This latest poison was supposed to be ten times more effective than the last. And the next one? Ten times stronger still.

Yushiro had called her a fool.
“I don’t know what you expect from this, Shinobu. Let the past rest. You’re only putting yourself in danger, like the last idiot!”

Her “brother” worried in his own strange way, she knew that. But tonight, she would prove him wrong—him, Tamayo, and everyone else.

When she had arrived five years ago, she had nothing left. No home, no hope, no future.

No sister.
No purpose.

Too weak, too fragile to behead a demon. Unfit to be a demon slayer.

All she had was her anger.

Her first impulse had been to kill Yushiro. Perhaps she would have known how. For two years, she searched for a way, while her delicate body stubbornly refused to grow stronger.

Her second impulse had been to run. But the young man had stood still, neither attacking nor retreating, watching her carefully.

Her final impulse had been to collapse, exhausted, to give up.

She had left everything behind, only to realize that she could no longer be part of the Demon Slayers. They wanted her to continue her sister’s legacy in another way—anything but wielding a sword.

————————————————————

 

“Shinobu,” the Master had said, his voice heavy yet kind, “we are endlessly grateful for your courage, for your dedication. I thank you for coming here today, despite your grief. I mourn Kanae as deeply as you do; she was beloved to us all.”

He paused, as if searching her soul.

“After long discussion, we have reached a decision. Regretfully, a Demon Slayer who cannot behead a demon is too great a risk. Your anger clouds your judgment, and this was not Kanae’s wish. She would not have wanted your path to end in ruin.”

The words cut deeper than any blade.

“However, you are always welcome among us. Your skills in medicine are invaluable. Kanae spoke of you with the deepest pride and love. You will always have a place as the head of our medical corps. Keep that in your heart.”

———————————————————

Too weak. Not enough.

With grief, rage, and crushing self-hatred, she had stood up, turned her back, and walked away without a word.

She had nothing left. Everything had been stripped from her.

Why even fight?

I’m coming, Kanae…

“Go on then, demon,” she whispered, eyes squinting shut, awaiting the release of death.

But it never came.

She must have looked pitiful, desperate, a shadow of herself. Yet that day, unwillingly at first, she had found a new home.

What irony.

 

The last houses and alleys slipped past her as she walked. Two residents had vanished in the past three days.

A wild animal, people whispered.

But the doctor knew better. She almost pitied the pathetic little demon bold enough to approach her city. Almost.

Eighty-nine experiments, seventy-four successes—tonight would be the seventy-fifth.

She hummed happily, unnoticed by the figure approaching… until a firm hand gripped her wrist, pulling her back.

 

“It’s dangerous out here. Go home.”

The audacity. Two missing residents, rumors of a wild beast, and midnight besides—yet she strolled toward the woods as if for a casual evening walk.

Foolish naivety.

Her lips curved into a flawless smile. “Hm?~”

Dark lashes, violet-tinted hair, porcelain skin, red lips, amethyst eyes. She looked like a delicate doll. Fragile, elegant, dangerous in her innocence.

“Hello, handsome. Aren’t you a sight! Need any help?”

Her voice was sweet, but something was… off.

Giyu stared, dumbfounded.

She stepped closer. “Helloooo? Anybody home?”

Another step. Too close.

“Did I take your breath away? Or are you deaf? Poor thing!”

“No,” he said, voice tight.

“Oh! Relief! Not very chatty. Well, handsome stranger, it’s been lovely, but I’d appreciate if you let me go now. Busy woman, you know?”

“It’s too dangerous. Go home.”

“Don’t worry, I’m a big girl. I can take care of myself. Promise.”

“The wild bea—”

“The WiLd BeAsT,” she interrupted, mimicking him.

“Don’t worry about the demon. I’m prepared! See?” She shook a little pouch of wisteria. “No monster’s getting near me!”

“…?”

“Not what you expected?” She tilted her head. “Okay, try this—Oh no! A demon? I’m so scared! Please, mighty handsome demon slayer, save this poor maiden in distress!”

Giyu blinked, still gripping her wrist. His eyes narrowed slightly, trying to make sense of the whirlwind in front of him.

Who the hell is this woman?

he wondered, irritation flickering under his calm exterior. Her presence was like nothing he had encountered before: delicate, deceptively fragile, yet utterly unafraid.

Shinobu, sensing his hesitation, let a small smirk curl her lips. “Are you a little slow, maybe?” she asked, her tone dripping with sarcasm. “I bet your colleagues don’t like you very much.”

Giyu froze, a flash of surprise crossing his otherwise stoic face. Then, after a long pause, he replied dryly, almost muttering, “People like me.”

A silence fell. Shinobu arched an eyebrow, tilting her head slightly. “Seriously? That’s all that stuck in your mind?”

Giyu’s grip on her wrist didn’t loosen. He could not risk letting her wander into danger. I can’t let her get hurt, he thought, tension coiling in his chest. Even if I don’t know what she’s planning… even if she’s reckless… I can’t let her go.

Shinobu, sensing that she would need a more dramatic touch, decided to try a different tactic. Her violet eyes widened, voice trembling, eyes darting behind Giyu. “Did you hear that?… No… oh no… stay very still… it’s there… the demon… in the alley, over there!”

At her words, Giyu immediately released her wrist. His hand flew to his sword, every muscle tensing as he scanned the alley for movement. His mind raced: Where? Where is it? I can’t see anything…

But the alley was empty. Nothing. No demon.

He blinked, confusion tugging at the edge of his composure. His eyes snapped back to her, only to find… she was already gone, sprinting down the street, her small figure fading into the distance.

“Goodbye~” her voice called over her shoulder, light and teasing.

Giyu froze, momentarily dumbfounded. How—how did she move that fast? His eyes followed the spot where she had vanished. No human could move like that. Is she…?

He exhaled sharply, running a hand through his hair, mind racing as he tried to make sense of the impossible. She had been right there—foolish, audacious… and gone in an instant. That woman… I don’t know what she is… but I have to keep watching her.

Even as frustration and confusion gnawed at him, he felt a reluctant admiration. She was reckless, clever, infuriating. And somehow… impossible to catch.

Giyu had tried to follow her, his movements precise, silent, like a shadow on patrol. Yet in moments, she seemed to vanish into thin air. Every turn, every corner—empty streets. Impossible… she can’t just disappear like that, he thought, tension coiling in his chest. Frustration bubbled under his calm exterior.

Finally, he let out a soft sigh and shook his head. Focus on the mission. That’s all that matters. He tightened his grip on his sword. There was a demon to kill, and no distraction—no matter how reckless, infuriating, or audacious—would stop him from doing his duty.

__________________________________

 

A soft breeze carried the scent of iron and dust as she crouched beside the demon sprawled on the ground. Her lips curved into a delighted grin. The poison had worked perfectly. Its effect was subtle, precise, and utterly fatal. She could almost hear the thrill of success humming through her veins.

“Perfect…” she murmured. She was reaching for her medical kit, ready to take blood samples, when a familiar shadow fell across her.

“Halt. Stay away from him. I’ll handle this,” Giyu said, stepping into her line of sight, his posture tense, hand hovering near his sword.

Shinobu tilted her head, eyes sparkling with mischief. “Hmmm?- ah! the silent guy that no one likes ! Miss me enough to follow me here?” She fluttered her eyelashes. “Well, the demon is definitely dead, so thanks, but you’re clearly not the fastest.”

Giyu’s jaw tightened. “He’s not dead. Step away.” His eyes, sharp and wary, stayed on the body. Don’t underestimate him… even if he looks gone, a demon’s life is dangerous to assume.

“Not dead? Oh no~? Haha!” Shinobu’s voice was rich with irony. She crouched down and lifted one of the demon’s arms, effortlessly.

Giyu stiffened, stepping closer, a hand rising to intervene. But nothing happened. The demon remained motionless, utterly still. His brow furrowed. That’s… not right…

Shinobu smirked. “You mean this one?” She demonstratively lifted the demon’s arm slightly. “This one?”

Giyu’s eyes narrowed, wary, but he stayed silent, unsure how to react.

“Hmm… not quite?” Shinobu tapped the demon gently with the tip of her shoe, just to emphasize the point.

Giyu’s confusion deepened. How is this possible?
The calm, analytical part of him fought to reconcile what his eyes told him with what logic demanded. The demon should have been dangerous, still fighting… yet here it lay, utterly neutralized, almost unnervingly intact under her playful handling.

So, another one...
he thought.
He'd heard of such cases before, but seeing it was different.

Shinobu glanced up at him, her grin widening. “You seem confused“

Giyu’s eyes never left her, sharp and piercing. “Was that you?” he asked finally, his voice low, cautious.

Shinobu shook her head, a faint smirk tugging at her lips. “Nope,” she said casually, though her eyes flickered with something darker—resentment. A simmering anger that had never fully left her since the Demon Slayers had essentially cast her aside.

Giyu’s gaze sharpened. “Then… what exactly happened here?”

She crouched beside the motionless demon again, her fingers brushing lightly over the corpse. “He was already… done for,” she said lightly. “I’m just curious. You know, old habits. Doctor instincts.”

Giyu’s brow furrowed. “Curious? By handling a demon like this?”

Shinobu tilted her head, letting her violet eyes glint in the dim light. “Curiosity is part of the job, you know. I couldn’t help but examine him. Look for anything interesting… and well, I suspected he had been poisoned.”

Giyu’s eyes narrowed, studying her carefully. Poisoned…? Could it really be her doing, or is she exaggerating? His mind raced, calculating. It’s suspicious, and yet… she seems oddly calm for someone standing next to a fallen demon.

Shinobu continued, her voice smooth and confident. “Judging by the state of his body and how he collapsed… I’d say he was exposed to a toxin. Probably quite potent. That’s what piqued my interest. Medical curiosity, nothing more.”

Giyu’s hands remained ready on his sword, still tense. “And you’re telling the truth?”

Her lips quirked into a small, knowing smile. “Honestly? I am. Mostly. But don’t take my word for it. See for yourself.”

After a pause, she stood, brushing dust from her sleeves. “I think I’m done here. Time to go.”

Giyu, however, didn’t move. His piercing gaze followed her, unyielding. “I don’t fully believe you.”

Shinobu let out a small, soft laugh. “Ah, the silent type… always skeptical. I expected nothing less.” She adjusted her bag, preparing to leave.

Giyu’s hands clenched, then relaxed slightly, still not entirely convinced. “Even so… don’t leave recklessly.”

Shinobu smirked, her voice dripping with playful sarcasm. “Reckless? Me? Well, you don’t know the half of it, Mr. ‘People like me.’ But thanks for the concern, really.”

And with that, she melted into the shadows of the forest path, leaving Giyu standing there, tension coiled and mind racing. She’s not just reckless… she’s… something else entirely.

Shinobu moved silently through the forest, her steps light, almost dancing over the soft earth. The thrill of the experiment still hummed in her veins. Her poison had worked perfectly—the demon’s fall was smooth, controlled, and predictable. A soft, delighted laugh escaped her lips.

Medical curiosity, yes… but also… satisfaction.

 

Shinobu paused, glancing back over her shoulder. Her violet eyes flicked briefly toward where he stood, a teasing smirk tugging at her lips. “You’re still there, huh? Watching me? Or just frozen in confusion?”

The Hunter‘s gaze remained steady, unreadable.

She chuckled softly, shaking her head. “Well, don’t worry, Handsom. I’ll leave“

 

Alone, Giyu exhaled slowly, the tension in his shoulders relaxing only slightly. His mind replayed every motion, every word. She’s not a normal threat… nor is she an ally. But I can’t stop watching her. Can’t stop thinking… what’s her next move?

The night was quiet again, yet somehow heavier. He tightened his grip on his sword, eyes scanning the treeline where she had vanished. The night was far from over.

Shinobu’s footsteps were light on the path, almost imperceptible. The night air was cool, carrying the distant scent of the city she was returning to. Her grin widened as she thought about how perfectly her plan had gone tonight. The demon neutralized, the poison tested, her curiosity satisfied.

All in a night’s work, she murmured, brushing a stray strand of violet-tinted hair from her face.

From the shadows behind her, Giyu’s eyes followed silently. His grip on his sword was loose for the first time since he spotted her, but his senses were still alert. She’s fast. Too fast. And reckless. That smile… that tone… I can’t predict her. And yet…

Shinobu tilted her head, as if sensing him. “Still tailing me, silent type? Can’t help yourself?” Her voice was soft, teasing, carrying just enough mischief to rile him.

Giyu’s jaw tightened, expression unreadable. She’s provoking me. Again. He stayed silent, watching her move, analyzing, calculating every step. Every motion is deliberate. She wants to see how I react…

She laughed lightly, almost to herself. “I have to say, watching you worry is almost… amusing.“

Giyu’s brow furrowed slightly, a flicker of something unspoken crossing his face.

————————————————————

The streets of the city were quiet again, lanterns flickering as the last few vendors packed away their stalls. Shinobu slipped into the familiar alleys with the same grace as a shadow. Her steps were unhurried, but her mind was still buzzing with the memory of the night’s “experiment.”

Passing two gossiping women, she caught fragments of their conversation.

“…two gone already…”
“…a wild animal, surely…”
“…shouldn’t let our children out—”

Shinobu’s lips curved into a sly smile. “Wild animal,” she whispered under her breath, her tone dripping with irony. If only they knew.

As Shinobu walked on, she couldn’t resist a soft laugh. Humans cling to such fragile illusions. But perhaps that’s what keeps them going.

Her laughter faded as her thoughts darkened. Unlike me. All I had left was anger—and the need to prove them wrong.

A familiar prickle on the back of her neck made her pause. She didn’t turn around, but she knew. “Still following me, Silent One?” she asked softly, her voice carrying just enough playfulness to mask the seriousness underneath.

From the rooftop across the street, hidden in shadow, Giyu’s gaze lingered on her. He didn’t answer—he never did—but his silence was louder than words.

She notices me every time, he thought. But how? And why does she let me know?

Shinobu tilted her head, violet eyes glinting as she walked on, her voice barely more than a whisper. “If you’re going to haunt my steps, at least try to be entertaining.”

Her figure slipped into the lantern glow, swallowed by the narrow streets, while Giyu remained rooted above, torn between duty and the strange pull this woman had on him.

For several streets, Shinobu could feel it—the weight of his presence. Giyu was still there, following at a distance, as silent and stubborn as a shadow.

She sighed dramatically, her smile curling into something mischievous. Persistent, aren’t you? I should give you points for effort… but even shadows need a lesson now and then.

The lanterns ahead marked the entrance to a women’s bathhouse. Without hesitation, Shinobu slipped inside, her step as light as a butterfly’s wing. Just before the door closed behind her, she glanced back—her violet eyes locking onto his silhouette on the rooftop. She stuck out her tongue playfully, a childlike, mocking gesture, before disappearing into the warm glow inside.

Minutes passed.

Steam filled the air as Shinobu let her hair down, the glossy black strands with violet tips falling loose around her shoulders. She changed into a simple robe, blending into the other women with ease. The insect-like huntress was gone; in her place stood someone ordinary, unremarkable. Someone he would never pick out in a crowd.

Outside, Giyu lingered on the roof across the street, unmoving. His eyes narrowed. She knows exactly what she’s doing. Toying with me… mocking me. And for what?

He exhaled slowly, shaking his head. The demon is dead. That should be enough. Whatever games she plays… they are not my concern.

And with that, he turned away, vanishing back into the night, his thoughts heavier than before.

———————————————————-

An hour later, Shinobu arrived at the modest home hidden in the quieter quarters of the city—the place she shared with Tamayo and Yushiro. The moment she stepped inside, the playful mask she wore outside began to crack.

Tamayo looked up from her writing desk, her gentle eyes soft with both relief and worry. “You’re late,” she said quietly. “Was it dangerous?”

Shinobu smiled faintly, but it lacked the sparkle of her earlier grin. “Not dangerous,” she replied, setting down her satchel. “Just… enlightening. The poison worked.”

Yushiro scoffed from the corner. “Enlightening? You risk your life for experiments and call it enlightening. One day, Shinobu, you’ll push too far.”

Her violet eyes darkened, her tone sharp for just a heartbeat. “Too far? I’ve already lost everything once. If I don’t keep pushing, then what am I even doing here?”

The words hung heavy in the air. Tamayo’s face softened with sorrow; Yushiro turned away, unable to answer.

Shinobu inhaled, steadying herself. When she spoke again, her voice was gentler, but her hands trembled faintly as she unpacked her notes. “I’ll make it work. I have to. It’s the only way to honor Kanae.”

The warmth of the bathhouse, the mocking laughter, the playful tongue she’d stuck out at Giyu—it all seemed like another life. Here, there was no mask. Only determination. Only grief.

———————————————————-

The forest was quiet again, save for the whisper of leaves stirred by the night breeze. Giyu moved swiftly along the path, his haori fluttering behind him, his hand resting lightly on the hilt of his blade. His orders were clear: eliminate the threat in the area, ensure the townspeople’s safety, and report back.

Simple. Straightforward.

And yet… his thoughts refused to obey.

The image of her—violet eyes glinting, that mocking little smile, the way she had stuck her tongue out like a child before vanishing—kept flashing across his mind. He scowled, tightening his grip on the sword. Why am I wasting time thinking about her?

His pace quickened, as if outrunning his own distraction. She’s reckless. Arrogant.

And still…

The memory of the demon’s corpse haunted him. Poison. That was no ordinary weapon.

 

He stopped briefly, closing his eyes, drawing in a slow breath. The night air was cold, sharp, grounding. Focus. My mission comes first. The rest is irrelevant.

But even as he pressed forward, blade ready, the doubt lingered. He had seen many things in his years as a Demon Slayer—blood, death, despair. But never someone quite like her.

Her voice echoed in his head, taunting, sing-song, impossible to ignore.

————————————————————

Shinobu sat cross-legged at a low table, papers spread neatly before her, brush in hand. Vials clinked as she shifted them, recording the details of last night’s experiment.

Tamayo poured tea, her quiet gaze lingering. “You didn’t sleep,” she said gently.

Shinobu smiled faintly, her voice light. “There was too much to write down. Dosages, reactions, collapse time… everything aligned perfectly.”

Yushiro snorted. “Perfect? You risk your life for corpses and call it perfect.”

Her laugh was bright, almost too bright. “Of course. Beauty is in the details, Yushiro. Even in death.”

But as her brush moved across the page, her smile thinned. Her thoughts drifted back—five years, the heavy silence of the Hashira conference, the sting of their verdict. Too weak. Too dangerous. Not Kanae’s wish.

She remembered Sanemi’s eyes, full of guilt and respect as he voted against her. Gyomei‘s quiet, fatherly voice—protective, but condemning. And then… Giyu. Newly made a Hashira, eyes downcast, saying nothing. Neither for her, nor against. Just silence.

Cowardice. Or indifference.

Her brush pressed harder into the paper, ink bleeding where it shouldn’t.

And now, five years later, he had stood right in front of her. Looked into her eyes. Gripped her wrist. And hadn’t recognized her at all.

“Good,” she whispered to herself, so softly that neither Tamayo nor Yushiro heard. Better that way. The last thing I need is the Corps knocking on my door again.

Her voice rose back into its cheerful lilt. “Anyway, the poison worked flawlessly. That’s all that matters.”

But in her chest, a mix of bitterness and satisfaction burned.

****************************************

 

„I could play nice or I could be a bully
I'm tired and angry, but somebody should be
"Come on, little lady, give us a smile"
No, I ain't got nothin' to smile about
I got no one to smile for, I waited a while for
A moment to say: I don't owe you a goddamn thing!
I, I keep a record of the wreckage of my life
I gotta recognize the weapon in my mind
They talk shit, but I love it every time
And I realize
Someone like me can be a real nightmare, completely aware
But I'd rather be a real nightmare than die unaware“

-Nightmare by halsey