Muzan x sister reader

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Night came. The crickets chirped as the darkness looked the place.

Y/n stood under the moonlights's glow and frowned. She still felt sad about Ubuyashiki's answer last morning.

"E-excuse me, Y/n-san?"

Y/n turned to see the demon carrying demon slayer, "Tanjiro...right?"

Tanjiro smiles and walks over to her, "Yes"

"Why are you here? Where's your sister?" She asks. Her eyes staring at him.

He blushes" N-Nezuko is with the others" he stuttered.

Y/n hummed before turning and walking away, "Ok then"

Tanjiro paused before jogging after her, "U-um wait!" He called out and walked infront of her. Blocking her way.

She stood and tilted her head, "What is it, Tanjiro?"

"Can Muzan change demons into humans?" He questioned, wanting to know if there was a chance that even Y/n can do it.

Y/n wondered, "Dunno...Onii-sama never really did any of that particular...why?" She asked before walking past him.

"I want my sister to turn back into human! And I was wondering if—

"If Onii-sama or I can turn her back right?" She cuts him off.

Walking beside the demoness, he hesitantly nodded.

She giggles before grabbing his hand, "Follow me, I'm gonna show you something—

"You brats, where are you going?" Sanemi spoke from behind them.

Tanjiro turned, he didn't want to be in trouble again. While Y/n only smiled and jogged over the hashira and snatched his other hand.

"W-what the?! Let go-

"Shush!! We're going to play!" She whined before dragging the two behind her.

Tanjiro glanced at her, "W-what are we gonna play,Y/n-san?" He asked while being tugged forward.

"Quiet! The others are sleeping!" She exclaims sternly.

Tanjiro glanced at Sanemi who grumbled, he couldn't remove the demoness's hand as he didn't want her tattling on Ubuyashiki.

Y/n removes her hold on Tanjiro, trusting that he'll follow her.

They reached the Ubuyashiki's main house. Sanemi stepped back, hesitating to go in his master's home.

Y/n slides the door open and turned to the younger demon slayer, "Tanjiro! Get in!" She whispered.

"O-oh..." walking in the open door, he removed his slippers and left it out, not wanting to dirty the clean house.

Y/n walked in and forcefully tugged the hashira.

"Geez! Let go woman! I'm not going anywhere! " he complained, glaring at the hand holding his hand.

The demoness glanced at him and let's him go, "Ok"

The both of them removed their slippers and walked in with their socks.

The two demon slayers followed the female, muffling their footsteps, not wanting to wake the family.

Instead of being discreet, Y/n hopped. Sending thumps making the two nervous.

Sanemi pulled her long sleeve. Y/n turned to him in confusion, "What is it?"

He glared at her, "You just said to be quiet! Why the he'll are you hopping?!" He whispered at her angrily. Tanjiro only stood to the side and watched, nervous.

The demoness rolled her eyes, "Duuuuuh~ Oyakata-sama and Amane-san knows I don't walk so quiet. They grow very suspicious and immediately wakes up" she stated.

She remembered the first time she tried sneaking out...a memory...

///////

Y/n tip-toed on the quiet hallway. She can hear their soft silence snores and smiled.

The thrill of getting caught rushed through her veins. She never tried this.

Behind her, stood a young man.

He stared at her ridiculous walking and chuckled.   "What are you doing, Y/n?"

Y/n paused and turned to him. Pushing a finger against her lips, she glared at him playfully. "Shusshhhh!! C'mon Kaguya! I thought you wanted to see the stars??" She asked the young Ubuyashiki.

He smiled at her, "of course I want to...but we might get into trouble--

"Don't care! Why? You tired?" She asked, worried about her friend's health.

He nodded weakly, "I suppose"

Y/n grinned, she was in her child form. The Ubuyashiki lead had told her to be in the same size or smaller than Kaguya just for safe keeping.

The demoness jogged to him and carried him bridal style.

"What are you doing, Y/n?" He chuckles, always forgetting that she was much more powerful than she looks.

She giggles and runs out the house, her loud thumps asked the lead Ubuyashiki and his wife.

"Don't tell me..."The previous Ubuyashiki lead muttered.

His wife only giggled and pats his back gently, "Don't worry, Y/n is with him"

He sighed,"That's exactly why"

///////

Soon, Y/n paused and stood outside the door leading to the basement.

"We're here!" She exclaimed happily.

Tanjiro stared at the door and smelt the ground, "It leads to the ground??"

Y/n slides the door open, Sanemi stared in surprise, he had thought it'll be room but all he saw was stairs leading down.

"What is this? A dungeon?" He sarcastically asked the demoness.

Tanjiro glanced at her, smelling the sad aura. But despite that, Y/n still wore a smile on her face.

"Well... It's supposed to be a dungeon right? I only call it a 'room' 'cause calling it dungeon would be too sad" she replied, 'happily'

Sanemi knew the boundary and shuts up. Not wanting her to have a tantrum the Kakushi's earned him about.

Basically, after the hashira meeting had ended. The Ubuyashiki's sent out individual Kakushi's who takes care of Y/n and let them explain what to do and not to do.

What to avoid and what to say. At first, Sanemi thought it was stupid. But seeing the emotion of fondness in their eyes let's him shut up and just take the information.

Y/n grabs a lantern and walked down the stairs  "Be careful guys. The stairs are quite slippery" she added before continuing down.

Tanjiro nodded while Sanemi grunted.

Reaching the bottom of the stairs was a metal door.

"A metal...door?" Tanjiro muttered.

Y/n turned to him, "Why? You thought they'll just let me have freedom?" She asked, sarcastically.

Tanjiro waved his hands, "A-ah no! I just--

"Shut up, let's just go in. We don't have all day" Sanemi grumbled impatiently.

Y/n frowned which was unnoticed by the two and quickly changed into a smile.

"Of course!"