The Deadly Woman (Yandere KNY x F!Reader)

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Thud

"OW! How the hell-"

Thud

"Ack!"

Thud

"(L/N)- san wins!" Tanjiro shouted.

Zenitsu stared at (Y/N) with a scared and shocked look. "Is nobody scared about how she just threw Inosuke to the floor three times in ten seconds!?"

Inosuke groaned as he sat up, rubbing his back slightly. He reached over and grabbed his boar mask that had fallen off due to (Y/N) throwing him around.

Tanjiro smiled while looking at (Y/N). "(L/N)-san! I have a few questions!"

The woman looked over at him, staring at his kind red eyes. "No questions."

"Please!" Tanjiro bowed in front of (Y/N). "I want to know more about you and your breathing style!" 

With those words, Zenitsu and Inosuke quickly joined in, bowing in front of (Y/N).

(Y/N) looked at the trio with half lidded eyes. "Alright. You can ask some." She sat down, resting her chin in her hand.

The trio quickly sat up, staring at her with curiosity. Tanjiro asked his first question.

"How old are you?"

"18. Same as Kocho-san."

Tanjiro nodded before continuing. "What element does your breathing style come from? Thunder, wind, water, flame, or stone?"

"Good question." She closed her eyes, relaxing slightly.

"... So which one?" Zenitsu chimed.

"Don't know." She replied bluntly.

"What!? Then how am I, the great Inosuke-sama, going to find your weakness!?" Inosuke fumed, clenching his fist.

"Once again, I don't know. It's just a breathing style, does it really matter?"

Tanjiro sucked in his breath before clapping his hands over Zenitsu's and Inosuke's blabbering mouths. "Your breathing style is very unique and amazing, (L/N)-san!" He shouted, recalling when he watched (Y/N) test out her forms.

(Y/N) nodded, opening her eyes. "Thank you, Kamado."

"Ah, please, call me Tanjiro!" (Y/N) hummed in response.

"We should train more!" Tanjiro exclaimed, taking his hands off the two mouths. "Zenitsu, you're up against (L/N)-san!"

Zenitsu's eyes widened, ready to complain. He looked at (Y/N) in horror before suddenly pausing. He took in her figure, her patient uniform slightly tighter than theirs. "I'll fight (Y/N)-chan!" 

(Y/N) and Zenitsu stood, Inosuke and Tanjiro backed away. "Go!"

Zenitsu joyfully ran towards (Y/N), ready to 'tackle' her. (Y/N) stared at him before simply placing her hand out in front of her. Zenistu's body ran in place, his head being held by (Y/N)'s pale and slender hands, her fingers gripping his hair. 

Zenitsu looked up at her with a slightly terrified face. (Y/N)'s eyes widened. Her face became pale as she let go of Zenitsu's head and stumbled back. She placed a hand on her stomach.

"(L/N)-san?" Tanjiro said, "Are you alright?"

(Y/N) looked down at Zenitsu, whose face had become more terrified. Her breathing quickened slightly as her eyelids constantly opened and shut. 

"Imoto-san!"

(Y/N)'s eyes rolled back into her head as her body fell to the floor. 

"Kocho-san!" Tanjiro shouted as he rushed to (Y/N).

The world became a blur to (Y/N).

"Muzan-sama." Gyokko said as he lowered his head in front of the demon king's presence.

Douma smiled as he looked at Gyokko, knowing something interesting would happen.

"Speak, Gyokko." Muzan's voice erupted from the ceiling. The man poured a vile of blood into a beaker.

"I have overheard a lowly demon cursing about his brother dying to a demon slayer, a Hashira." Gyokko giggled, two of the many hands on his body covered the mouths in the place of eyes.

"That information is worthless-..." Muzan paused his curse towards Gyokko.

"Ooo~ Tell me the news Gyokko! Tell me dear friend!" Douma cupped Gyokko's face, smiling at him intensely.

"What is the information, Muzan-sama." Akaza spoke up, clenching his fists at the sight of Douma.

"That wench really thought she would win!? I'll kill her! I will kill your daughter you wench! I will tear her limb from limb, gouge her eyes out, break her bones, and rip her heart out! You damn wench!" Muzan's sudden outburst made all the Upper Moons stop their actions, listening to his anger. Veins were noticeable everywhere on Muzan's body.

"What angers you, Muzan-sama?" Douma asked before his head fell to the floor from being cut off.

Muzan breathed heavily, gripping his black hair. "The Umi family... The bloodline continues..."

"How is that possible? I killed Kai (L/N), and his sons perished in the fire." Hantengu said, trembling on one of the many staircases in the Infinity Castle.

"Did you not hear me!? Worthless demon! Kikamae had a daughter! A damn daughter! A worthless, damn, bloody fucking daughter!" Muzan shouted. "Who knows what she will be capable of!? Gyokko has told me that the daughter is a Hashira! If she is a Hashira, we could all be in danger! That bitch could be as powerful as-" Muzan stopped himself from saying anything more, closing his eyes and digging his nails in the table holding the many chemicals and beakers.

Daki stayed hidden in the darkness, afraid of Muzan and the anger. 

Douma opened his mouth to speak but was quickly cut off. 

"The girl has most likely matured into a young adult, depending on her age the night Hantengu set fire to that village." Kokushibo's voice erupted from a small room somewhere in the endless castle. "Though, Kikamae's eldest son was 12 then, which would mean the daughter is 18."

"Ah, what a tender age for a woman." Douma cooed.

Akaza looked up at Muzan. "So, what do we do Muzan-sama? Everyone here has met an ancestor of Kikamaes. We all survived. An Upper Moon can kill her with ease. She is only a young adult, a teenager at that. She is not fully developed. It would be impossible if she had full strength, mentally and physically."

"You wouldn't kill her, would you Akaza-sama? You don't kill women." Douma questioned, his rainbow eyes shining.

"Enough, all of you." Muzan commanded. He rubbed the bridge of his nose before suddenly smiling.

Dwang

At the strike of a biwa, all the Upper Moons were teleported to a large library. Muzan held a book, smiling more.

"That bitch is the key."

Muzan looked at the Upper Moons.

"Find that (L/N) and bring her to me, alive and well."