Muzan x sister reader

Total constant

Y/n spent the whole day with the kamaboko squad.

The boys were so exhausted talking with her that once their heads hit their pillow, they were knocked out.

Though unbeknownst to them, Y/n was only wasting time for their recovery. Buying time for everything is her specialty. Her role in their eyes was of a powerful demoness yet stupid.

Unclenching her fists under her sleeve, her bright smile disappears as she stared at the small window that was placed underground. There shone the moonlight.

"...Hurry up Onii-sama..." She mumbled, clasping her hands together as she continued staring up the full moon and basked in its light.

Closing her eyes, she breathed evenly.

Total concentrarion breathing, constant

She felt air stiff up around her. The fact that the one who had taught her such an important technique was no other than the Tsugikuni twins.

One was by memory and one was by personal.

Only a month after Yoriichi had captured Y/n. He was supposed to be removed from the corps, but since he had caught one of the proeginators, he was granted by his peers over 5 month stay and he'll have to go after that.

"Relax your upper body... tense up your bottom half" A deep mellow voice commands.

His fluffy brown hair flowing behind him as his red coat flowed as the wind go through. His sword attached to his hip. Maroon eyes staring at the breathing demoness intensely.

"You got it, Y/n?" He asks, crouching at her level.

The demoness nods, trying to keep the annoying technique up, "I-I think so" she groaned.

Staring at her with his dull eyes, he pulled his hands back and smacked her in the stomach. Air was knocked out of her as she landed on the ground by her back.

"Are you ok?" He asks her, bending down and lending out a hand to help her up.

She glared at him annoyingly. "Are you serious right now?! I said lightly smack me!" She fumed, still accepting his hand and was pulled up effortlessly.

He tilts his head, confused as he stepped back. "But I did lightly smack you" he says.

An irk mark appears on Y/n as it was as if she's talking to a clueless child, "This kid doesn't even know how to control his strength" she thought, glancing at his hanafunda earings.

"You just punched me! My rib got cracked you know!" Y/n groans, glaring at him playfully.

It's was as if he was a switch. He looks down and a depressing aura surrounds him as he sat on  corner, his knees pulled tightly to his chest.

"I'm s-sorry..." he whispers guiltily.

Her lips form a straight line, "Goddammit, Why the hell does he need to be so cute" she cried in her thoughts as she looked at the grown man.

Sighing, she walked to him and pats his back, "Someone you might want to know will appear to you tonight once you go hunting. I don't know if you'll feel anger... but consider it a gift" she muttered to him.

He glanced at her with his dull eyes now full of confusion, "What?"

She pinches his cheek, a blush on her face, "Just be ready for your hint later!" Y/n exclaims before hopping up and disappearing, probably over to her room.

Y/n hummed in her room, thinking about the memory only to frown. She doesn't remember who she had stationed out that night.

"But I think it was related to a girl or something" she thought before walking go the door and walks up the basement.

As she stepped a foot on the original floor, she notices a sleeping F/n.

"Are you serious? Didn't I tell him to stop taking the nightly shifts?" She groans before removing her haori and gently placing over his shivering body.

"Geez, you work you ass of too hard" she mumbled.

Turning away, she hopped down the hall and made her way outside the garden and smiles fondly as her red eyes land on the bright coloured fireflies.

Reaching out her pale hand, numerous fireflies lands to it. Her hand was now bright as their light.

In a split second, she snaps her hand close, crushing the bugs in her hand.

"I'm hungry..." She mumbled before wiping her dirty hand on the small stream of water and didn't bother washing it dry.

Strolling around the garden, she sees a black hair pop out in the corner of her eye. The familiar design of the mismatched haori made her smile brightly.

Y/n hops to the direction of the man before jumping. She looks down to see the mismatched hoari.

"Oh! I remember now, he's Giyu!" She thought excitedly and lands gracefully behind infront of him.

"Hello Giyu--

"Are you spying on me?" He cuts her off, his eyes squinting at her suspiciously.

The demoness pouts and crossed her arms, "Oh how rude! I just noticed your haori ok?!" She says, annoyed at his eyes giving such a doubtful look.

Humming, he nods, "Ok" he says before going past her.

Her mouth agape at the short conversation, she pouts and ran to him.

"Hey you meanie! We're not done talking yet!" She fumed, her cheeks puffed out as she walked beside him.

His eyes trained forward and not giving a look to the demoness who grew annoyed at his ignores.

She tugs his haori, frowning, "Hey! Giyu! Don't be so mean! Talk to me!" She huffs, her tugging goes harsher and harsher.

Suddenly, as she tugged again, she couldn't control her strength and pushed him to the side. Her eyes widen and she immediately dived down to cushion his fall.

Y/n huffs as his body behind lands on her back, "You ok, Giyu?" She asks, looking at him at the corner of her eye.

Giyu's eyes were wide as his mouth was left agape. The scene he had encountered with Tanjiro when they first met played in his mind.

In his thoughts there played the same thought.

"...Maybe she's different..."

A/n

Oh my goodness.

Sorry for the late updates, I'm busy playing IDV right now. I'm also too lazy so yeah.