"This is a one-shot story I created, though there's a chance I may expand it into a full story.
[{3rd POV}]
The wind howled through the shattered windows of the house, dragging with it the chill of a gray English morning. The crumbling stone walls of the old cottage groaned in protest, ivy clinging desperately to its sides like veins on a dying corpse. Dust curled in the air, dancing in faint light beams that struggled through broken glass.
Inside, silence ruled.
Except for the steady, rhythmic sound of breath.
"Haa… Haa…"
In the center of what used to be a living room, a boy stood barefoot on the cold, cracked floorboards. His feet were planted wide, knees bent. In his hands, a carved wooden stick—splintered at the tip—moved like it weighed nothing. His body twisted, snapped, spun. A slash to the left, a sweeping cut to the right, then an upward strike followed by a sudden drop into a low crouch.
"Breath of the Wind..." he whispered, breath misting in the air. "Fourth Form: Rising Dust Storm..."
He moved with fluid precision, as if the air itself parted to avoid the edge of his strike. Dust exploded in a swirl as he finished, his body still, one knee on the floor, stick angled across his chest like a blade.
But there was no applause.
Only the hollow echo of wind moving through the bones of the forgotten house.
The boy stayed in that pose for several seconds before rising. His skin was pale, his body lean but wiry—muscles defined from constant motion. His white hair was untamed, falling into his eyes, and his face bore a long scar crossing from brow to cheek—an old memory he didn't remember getting, but one that had always been there. Just like the way his hands moved on their own. Just like the rage in his chest that he had no name for.
He exhaled, long and slow.
"I'm still too slow," he muttered in Japanese.
He wasn't sure how long he'd lived in the house. A month? A year? He didn't count the days. There were no clocks, no calendar—just cold mornings, bitter nights, and meals scrounged from trash bins in town or hunted in the surrounding woods.
They didn't know he was here.
They being the town nearby—the one where the people talked fast and loud in a language he couldn't quite understand. He picked up pieces—"Get out," "thief," "police," "crazy kid"—but they meant little. They didn't matter.
They weren't him.
He didn't know who he was, either—not really. His name? Sanemi. That part was clear. And he remembered other things too: blood, swords, demons, breathing styles. Pain. Loss.
But also duty.
A burning purpose that hadn't faded, even in this strange, cold place.
Sanemi raised his hand.
The room, already still, grew quieter—like the air was holding its breath.
With a sharp flick of his finger, a faint crescent shimmered in front of him. A split second later, a thin blade of wind shrieked through the air and carved a deep gash across the rotted plaster wall. Dust and fragments rained down, and the ivy outside swayed in protest, as though recoiling from the blow.
Sanemi narrowed his eyes and slowly opened his palm, studying it.
The wind gathered there—subtle, yet coiling with intent. Invisible threads spiraled in his grasp, condensing until the pressure tickled his skin like static.
He clenched his fist, and the wind answered.
It pulsed—tight, sharp, waiting for release.
Then he exhaled and let go.
The energy unraveled, vanishing into the air like breath in winter.
Even now, after all this time, it still startled him. This foreign energy—not the power of Nichirin blades or the breath techniques passed down through generations, but something new. Something raw, ambient, and ancient.
He'd felt it from the moment he woke up in this world—reborn, small, and furious. At first, it had made him ill. The air here was wrong, heavy with... something. It vibrated beneath his skin, made his breathing ragged, his focus slip. It wasn't demon scent. It wasn't fear. It was something he couldn't understand.
But Sanemi was not one to be conquered by anything—not even the laws of a new world.
So, he learned. Alone. Quietly.
Each night he'd sit under the broken beams of the house and breathe—deep, measured, deliberate. He'd reach with senses honed to survive, and test what bent to his will. The wind answered first. Always the wind.
Now, it obeyed him like an old companion.
He had taken the core of Wind Breathing, stripped it of its rigid formality, and fused it with this new, living energy that lingered in the air like pollen.
And now he had begun to shape it.
He turned his eyes to the broken wall, to the place his wind blade had struck. The cut was clean. Too clean.
"Still shallow," he muttered in Japanese. "Not enough force."
He would need to refine the flow. Increase the rotation of the pressure spiral before release.
Another project. Another night. More breathing. More focus.
Then something shifted outside.
He paused.
Not the wind. Not a rat. Something different. A flutter. A scratch.
A shadow passed the broken window. Then, silence again.
Sanemi moved soundlessly toward the door, stick still in hand, muscles loose but ready to coil.
A shape landed at the threshold with a soft thump.
An owl.
Brown-feathered, proud, with intelligent eyes that didn't blink. It regarded him with what Sanemi could only interpret as mild impatience, like a messenger long delayed and unimpressed with his current assignment.
Clutched in its talons was a thick envelope, yellowed with age but pristine, sealed with deep red wax pressed into a strange crest—an elaborate H encircled by a lion, snake, eagle, and badger.
The owl gave a low hoot and dropped the letter at Sanemi's feet.
He blinked.
"…A letter?" he said aloud in Japanese, confused.
No one had ever sent him anything. Not here. Not in this life.
Cautiously, he bent down and picked it up. The envelope was heavier than it looked, like it carried something important. The name on it was written in flowing, foreign script he couldn't read.
He turned it over, cracking the wax seal.
Inside was a parchment folded cleanly. He unfolded it carefully.
More lines of text—neat and precise, all in that same unfamiliar language.
Sanemi's eyes scanned the paper.
And again.
Nothing.
He couldn't read a word of it.
Frustration coiled in his chest like smoke.
"This language again," he hissed through clenched teeth.
The parchment crumpled in his hand as he slammed it against the cracked wall. The owl flinched but didn't flee, merely shifting its talons and eyeing him as if unimpressed by his outburst.
Sanemi dropped into a crouch, resting his elbows on his knees, one hand dragging through his tangled white hair.
He hated this.
The silence. The isolation. The constant barrier between him and the world around him.
He couldn't speak to anyone. Couldn't ask for help. Couldn't read a damn sign without guessing. Every word spoken in town came out warped and alien to his ears—muffled and twisted like sound underwater. Their language was sharp, slippery, and relentless. He had picked up scraps, sure—yells thrown his way, warnings muttered under breath, signs posted near shops—but never enough. Not enough to live.
And now this letter.
This... invitation, maybe. Or a warning. Or something far worse. He couldn't tell.
He looked at it again, his eyes tracing one word over and over: Hogwarts.
It stood out, bold and distinct among the squiggles and loops.
Something deep in his gut stirred.
His instincts—so sharp they sometimes spoke louder than thought—told him it mattered. That this name meant something. That behind this word was a place or a person that might help him make sense of the strange energy he had begun to command. Of why the wind now bent more easily to his will than ever before. Of why his body moved like it had never forgotten the battlefield—even in this fragile, younger form.
But none of it mattered if he couldn't even read the damn letter.
Sanemi let out a low breath—less a sigh, more a growl of weary resignation. He stood, slipped the envelope into his coat, and stepped toward the broken door.
The sky outside was iron-gray, and the morning wind had teeth. His coat was thin, his feet bare, but he didn't flinch. He never did.
The cracked steps creaked beneath his weight as he stepped outside. The ground was damp with dew, and the long grass whispered as he passed.
He had two goals today.
Find food.
And more importantly—
He clenched his jaw, eyes narrowing.
—Learn this cursed language.
If he was going to survive in this world—if he was going to understand it—he couldn't rely on instincts and stolen scraps of food forever.
No more guessing. No more waiting.
Somewhere in that town was a path forward.
And he'd carve his way through it, one step at a time.
Just like always.
A/N
I just want to make a few things clear.
There's a strong possibility that I'll turn this into a full story, though it may take some time to develop properly.
Second, I won't be including any kind of system mechanics. They just don't fit the tone I'm going for. Personally, I find them a bit overused—and, in most cases, kind of cringe.
(Of course, there are exceptions. Stories like Harry Potter: The Arcane Thief, Solo Leveling: My Hermes System, and a few others genuinely earned my attention and respect.)
Lastly, no other Demon Slayer characters will appear in the Harry Potter world. I won't be using them as a shortcut to "balance" power levels or to patch over plot gaps with forced crossovers. I want this story to stand on its own without relying on that kind of trope.
Also, share your Opinion here in the comment --->
Thanks for reading, my Superior Readers.