Kimetsu no Yaiba Sibling Scenarios

Sanemi X Little Sister Reader

Third Person P.O.V

"Sanemi! Nii-san!", (Y/N) yelled, calling to her older brother as he walked down the hallway of his estate.

He turned around, with a look that terrified her, making her freeze in place.

"I don't know how I am related to someone as weak and pathetic as you. Don't ever approach me, unless you want to have a broken limb.", Sanemi said, giving her a glare that chilled her to the bone.

"B-but, nii-san, I-", she was cut off when he grabbed the collar of her Demon Slayer uniform, and brought his face down toward her's.

"Don't, call me that.", he snarled, gritting his teeth, before throwing her down.

She grunted, and cried out when she landed on her wrist wrong. She pushed herself onto her elbow and looked at his back as he walked away from her.

That was when she let her tears fall. She looked at the small box she was holding, and opened it, staring at the charm she had made for him for his birthday. She closed the lid and stuffed the box into her pocket, and stood up, holding her wrist.

She walked to the Butterfly Estate to get her wrist checked, then left, only to be transported to a weird place, where there were different rooms everywhere.

She walked in one, holding her Nichirin blade and gasped. In front of her was the most horrific scene she had ever laid her eyes on. There were many Demon Slayers, dead, sprawled everywhere in the room, and in the center, was a demon holding a sword. The demon suddenly looked at her and grinned.

"Marechi.", he said, licking his lips. She stepped backwards, then pushed herself at him, unleashing an attack.

"Wind Breathing,First form:Peaceful Winter Gale!", she shouted, only for her blade to slice his arm.

She gritted her teeth and attacked again.

"Wind Breathing, Fifth Form: Deathly Whirling Tornado!", she yelled, but instead of striking him, he sliced her on her arm.

She grunted and held her arm, before running at him again. After battling for an hour, she was exhausted, and severely injured, yet, she still attacked. Only this time, he sliced her arm off, making her scream out.

Within a split second, he impaled her abdomen, and sliced her leg, making her cry out. She gritted her teeth and charged again, her sword aimed at his neck, but when she brought her sword down on his neck, it only broke her sword in half, making her gasp.

He smirked and stabbed his sword through her stomach, making her cough out blood, and fall to the floor. Just then, Sanemi ran into the room, gasping when he saw his sister lying on the floor, barely breathing, and a demon towering over her.

"Oi! Over here!", he yelled, and right as the demon turned around, he had already brought his sword through his neck, and sliced the demon's head off, instantly.

He rushed to his sister's side and held her in his lap.

"Nii-san? What are you doing here? I'm sorry. I'm sorry I was too weak.Im sorry I never made you proud.", she said, looking up at him.

He let out a sob, as tears streamed down his face. " No, n-no. You aren't weak. You know how I know? You put up with father, and you put up with me and my unbearable self. And, you did make me proud. I'm so proud of the person you became, despite me and father. So, please, don't leave me!", he sobbed.

She gazed up at him, as tears fell from her eyes, and she smiled.

"Nii-san.I-i never did give y-you your present.", she whispered.

He looked down at her in shock as she revealed a small box from her uniform pocket. She then put her hand on his face, and smiled again.

"You never really did hurt me. I, just wanted... to let... you know that.", she said, her voice getting quieter, before her hand fell to the floor.

His eyes widened, and more tears fell from his eyes, as he hugged her closer to him.

"Not you too. It can't be. First Genya, and now you? Please. Don't be true.", he sobbed.

He carried her out of the fortress, to near where the battle with Muzan was, and laid her on the ground. That's when he noticed something. She had a small smile on her face. He looked down at the gift that was in his hand, and opened it.

Inside was a jade charm, in a swirl shape, that was the color lilac, attached to a black cord. He gazed at it, before he opened the letter.

In the letter, she wished him happy birthday, and thanked him for teaching her to use a sword, and for raising her, even if he did show distaste towards her. After he finished reading the letter, he teared up again. He stopped, and tied the charm to the hilt of his sword, before joining the others in the battle of Muzan.

'We'll win, no matter what. I promise you that, (Y/N) , your death will mean something'.