Muzan x sister reader

Sword

Underneath the floors of the Ubuyashiki sat a crying demoness, on her hand was a knife. A clean knife.

Her sobs filled the room as she once again stabbed her chest, only for it to heal completely as she dragged it down her skin. Finally having enough, she rips the knife out of her chest only to scream in pain.

Thankfully, she had already placed a cloth in her ,push to prevent any of her screams to get out. Throwing the knife, she cries in her hands. Her tears pooling her palms.

"Why doesn't it work?! It hurts so bad! It's so painful!! I want Muzan-nii- " Y/n stops in her tracks, her eyes wide as she slowly covered her mouth.

"H-he's bad! He's evil! He's not the Muzan-nii I know!" She screams in her head. Tears fills her eyes as she looked down at her lap. "B-but he's still my brother. . ."

Her hands tremble before clutching her head in frustration. "Agh!! This is so confusing! Confusing! Confusing! Confusing! I don't know what to do!" Y/n screams, trying not to pull her hair out.

"I-If only I had S/n's smartness then maybe I would know what to be doing right now!" She whined, biting her nail yet again. "I don't like this!"

Suddenly, she hears footsteps just going over her room. Noticing the barely noticeable type of footsteps, she gasps. "A pillar!"

Immediately, she bolts up her room and dashes past the two twins that was stationed to keep her in. But noticing that she used her demon abilities to run out, they hurriedly went to their mother to report,

Y/n's red plum eyes lands quickly on a white haori with a pink butterfly ornament on the hair. "It's not a pillar?" Y/n thoughts before shrugging, "As long as I get that blade it's fine!" She thinks determinedly as she ran towards the girl.

The girl turn to her revealing her pink orbs which widened in surprise. She tries to duck but fails as the demoness runs past her.

Confused, she stood back up and looked around her only to see that her sword was gone. "My sword? But why that?" Kanao thought, confused,

+++++++++++++++

"Finally!" Y/n exclaims, in her room. She had quickly dashed back in her room as soon as her hands touched the sword.

Unsheathing the blade, she smiles happily. "Good thing Amane-san said that Oyakata-sama is sleeping! He can get a dream once I finish this!"

Pointing the sword above her right chest, she breathed out shakily before mustering up her courage and stabbed herself deeply.

++++++++++++++++

A scream pierced throughout the Ubuyashiki estate. Everyone inside all stopped all they were doing and glanced around, wondering where that came from.

But hearing that it was a female's they thought that it was Y/n's. They ignored it, knowing that it may be another tantrum.

+++++++++++++++++

Y/n's heavy panting filled her room, along with the bloody chunks of human heart that laid on the floor. Staining it,

The pink sword stained with human blood. The scent of the blood was decaying, irritating her nose,

Panting, Y/n stumbles up. She had forgotten how painful the sensation the swords gave. It's been decades, she had forgotten all about it.

Despite her energy and strength being completely depleted from just a single. . . Multiple stabs, her strength was quickly replenishing due to her being a demon.

"Let's get going. . . Before my time runs out"

++++++++++++++++++

Tanjiro sat ontop the roof of the butterfly estate. His chest slowly heaving up and down, mastering the technique of breathing,

Suddenly, his nose twitches and he immediately covers his nose, "This scent. . . Is an animal dying?" He thoughts. Not being able to handles the smell, he gets ready to hop down. But before he could even hop off, his shirt's collar gets grabbed and he's pulled up.

He groans but immediately stands up and tenses when his orbs lands on the frail looking demoness. "Y-Y/n-san?" Tanjiro called out only to cover his nose, "The scent's coming from her?!"

"T-Tanjiro. . . A sun breath user" Y/n smiles. "You just look like him" she continues, glancing at the familiar Hanafunda earrings which dangled on his ears.

His brows furrowed. "Sun breathe?"

Suddenly, Y/n's smile disappeared and is replaced by a serious face, "listen here, Tanjiro. You're the only one who can defeat him"

"Him? Do you mean Muzan?" Tanjiro mumbles.

She nods, "Yes! One has failed before and. . . You are the only one! You are the sun breathe user's descendant!" She exclaims enthusiastically.

His eyes widen. "You know about the breathing technique I talked about with Shinobu-san?" He asks.

"Of course I do, I've lived for years" Y/n giggles.

Holding the Hanafunda earrings fondly, a small soft smile appears on her face. "I have no time left. Muzan-nii's base is by the edge of the north. It's in the tallest building there." She suddenly tells him.

"W-wait what why are you just telling us just now-

"He has multiple hearts, use the see through world. It's in the diary that I hid from S/n. Under the floorboard"

"J-just wait-

"You guys have 80% chance of dying but that doesn't matter. You are a sun breathe user after all"

"Y/n-san!" Tanjiro shouts.

Her eyes widen in surprise. "W-what?"

"Slow down!" He sayw to her sternly.

Y/n grabs him by the shoulders. "Don't you get it?! I'm about to die! So unless you kill him then all of this are all for nothing!" She screams. "You have to kill my brother! You must!"

"He's bad! Evil! He's turning like mommy and daddy!" Y/n suddenly screams out as she shook him. "He's getting too greedy! He's being a monster!" She continues, tears springing put her eyes.

"Ever since that doctor gave us that medicine, he changed for the worse!" She sobbed, tears running down her face.

Tanjiro's eyes soften and pats her head. "Fine, What should I do?" He asks. "I can finally smell your emotion, Y/n-san. . . It's like a child's"