My Hero Academia/ BNHA Brother Scenarios/ One-Shots! X Reader!

'Attention' Overhaul X YANDERE Child Sister Reader!

(y/n)= your name

"Kai, come sleep with me!" Eight year old you said. Kai stroked your cheek. "I'm sorry. I'm busy now. Tomorrow, okay?" Kai responded.

You frowned. " 'Busy'? Busy making the Quirk-Destroying drug from Eri's blood? I don't like it...Kai, I don't like it that you're so busy..." You said and looked into his eyes. "Sorry, (y/n), but it's very important. This way, we'll repay boss for taking us in. It's for the yakuza to rule the underworld again, for Shie Hassaikai to get its glory back." Kai responded.

" 'Important'? More important than me?" You asked. Kai could hear a hint of sadness and dissappointment in your voice.

"No, no, no. Of course not!" Kai said and kissed your cheek. "Goodnight." Kai said and closed the door of your room behind himself.

'It's not fair...I don't like it...' You thought and slowly fell asleep.

Kai of course, already had noticed your possessive/ obsessive behavior towards him, but he didn't think much of it.- He thought it wasn't something he should worry about...

Next day:

Kai opened the door of Eri's room. "Eri-" Kai cut himself off as he saw you holding a bloody knife and Eri is nowhere to be seen.

Kai gasped and looked terrified.
"(y/n)...Where's Eri?" Kai asked as softly as possible, he didn't want to startle you.

You turned around and looked at Kai. Your dress had blood on it and a few drops of blood were also on your face.

You started crying. "I-it wasn't fair! Y-you were too busy with Eri! I h-hate Eri! So I...I killed her!" You shouted.

Kai didn't know what to do, you ruined his whole plan. Kai couldn't hurt you of course, because he loves you very much.

"Where is she...?" Kai asked, he stepped a little closer to you, but you cut him off: "Don't move!" You gripped tighter on the knife.

"Tell me where she is, (y/n)." Kai said, his voice was a little shaky. "It's too late, Kai. I even...cut her body into pieces...You can't heal her with your quirk anymore." You replied.

Kai fell on his knees. "M-my whole plan...Everything..." Kai said, his eye was twitching. His breath hitched: "It's ruined...(y/n)..."

You dropped the knife on the ground and walked to Kai. You hugged Kai. Kai was still too shocked about everything what happened, he was too shocked to return the hug.

"I love you." You whispered in his ear.