Not Alone || kny x reader

十四

Y/n watches from afar, how Tanjiro and Inosuke fight against a giant spider demon that plays as Rui's father. Y/n stayed far because of his creepy face but watched carefully nonetheless.

Getting bored by the lack of action she was doing, she left and wandered about in the forest. Y/n hears a sound but ignores it, that is until Tanjiro's loud crow got her attention.

"Help! Help! Four slayers in trouble at Natagumo Mountain!! One is missing! And three are injured!! Ke-ke!" It repeated this until it slowly faded into a distance.

Y/n felt uneasy for a reason she doesn't know, she starts looking for Rui. Y/n hears Zenitsu's cry in the distance but when she got there he passed out, and suddenly, he attacked the spiders that he had tried running away from.

Lightning came out of his body as the spider demon starts to get terrified "WHAT THE HELL IS THIS?! YOU'RE AN ENTIRELY DIFFERENT PERSON!!" He yelled.

Zenitsu then zoomed forward, up the tree and slicing the demon's head clean. Zenitsu lands on the roof of the treehouse and doesn't make a sound, Y/n walks up to the disintegrating body of the demon and climbs up the tree.

Y/n sees Zenitsu passed out but still trying to open his eyes. Y/n's hands roam his upper body 'he's been bitten by some sort of poison by that demon yet he manages to slay it..? Did I underestimate him?'

The girl notices the boy's body slowly shrinking, she made a mental note to find Muzan and tell him about the three boy's strength. Y/n hears Tanjiro yelling and then sees water come up from the nearby trees.

Upon getting there, Y/n's eyes widen as she hears Rui say "I want her as my sister, give her to me", she raised an eyebrow, Tanjiro tells him no and he attacks him again, Y/n then ran, unsheathed her katana and blocked Tanjiro's attack.

Surprising all Tanjiro, Rui, Nezuko and even herself. Y/n's eyes furrowed as she kicked Tanjiro by the stomach making him fly back to his sister, she made sure not to kick him too hard, just enough to get him to back off.

"Y-Y/n-san?! W-what are you doing??!" He asks, holding his stomach in pain.

The girl takes notice of this 'Right! He fought the giant demon, Rui's mother AND got toyed by Rui' Y/n mentally facepalms. Y/n positioned herself ready to fight as Tanjiro stood up, but the boy didn't attack, he just positioned himself ready to, but he couldn't move his body.

"You do realize that that demon is lower moon five right?! Why are you protecting him?!" Tanjiro tries to ask again.

"Onee-san.." Rui quietly says, Tanjiro's eyes widen in surprise 'sh-she knows him..? Is he her little brother??' Tanjiro's shoulders fall but not his defense.

"I told you I'll be fine" Rui says, tugging Y/n's haori. Y/n doesn't say a word but instead runs towards Tanjiro, clashing their katanas, Y/n kept on attacking and moving forward while Tanjiro defends himself moving backwards.

Suddenly Nezuko kicks Y/n from the side making her fly two trees farther from her and Tanjiro.

"Y/n-san!" Tanjiro tries to run to her but a web catches him "Nezuko! Help!"

"Come here now Nezuko..you can be part of my family, along with Onee-san" Rui puts his arm forward, expecting Nezuko to take it.

Nezuko runs up and tries to free her brother but gets stuck in the web, it tightens on her body and blood starts to run across it. Y/n on the other hand, slowly stands up, her lower abdomen aches from pain as she does so.

Y/n holds her katana tight, standing still, she looks up at the two siblings, then, the web bursts into flames, freeing both Tanjiro and Nezuko. Tanjiro runs straight to Rui.

"Water breathing..tenth form.." Tanjiro whispers but Y/n could still hear it, her eyes widen and she feels another emotion, worry "Constant Flux!" After saying this, a dragon that's surprisingly made of flames, appear and attacks Rui.

Y/n steps forward and groans as the pain gets stronger, she watches as Tanjiro slices Rui's head, breaking his katana in the process and then falling down, Nezuko rushes to him and Rui's head fall off.

At that moment Y/n couldn't do anything but stare, she knew Rui was still somehow alive, she could still feel his aura and he wasn't disintegrating like the demons usually do.

Y/n decides to ignore the pain, but found it hard, she slowly walked towards the two, Nezuko looks at her and hugs her, crying. Tanjiro just looks at her, still confused as to why she was protecting lower moon 5.

"Get your hands off of her!" Rui suddenly yells, the three turned to him and Tanjiro was shocked, seeing that Rui's head was back on his body, but now not with a calm face, more annoyed and angry.

Rui raised both his hands as if to attack but his head suddenly gets cut off and Tomioka standing beside him facing the opposite way. Rui starts to disintegrate as his head hit the ground, Y/n walked over and put a hand on his cheek.

"Onee-san...thank you..for...spending....time with.." With that, his head and body disintegrated into nothing. The white bracelet Rui had on his wrist fell to the ground and Y/n picked it up and put it on her own.

Giyu stares at the girl beside her "You have a demon brother too..?" He asks, feeling a little guilty for killing the demon but he knew it was what had to be done.

"I met him when Upper moon two brought him for a meeting with Muzan-san, he isn't my biological brother..but it was nice..while it lasted" Y/n mutters the last part as she starts to loose consciousness.

'Shit..I used too much of my energy...'

Tomioka and Tanjiro widens their eyes 'Did I hear that right? She knows Upper moon two and Muzan? Does that mean she knows other upper moons?' Both of them thinks.