I remember is about a girl(crazy mad and in love ) who tortures or threaten anyone to come near to the MC. During their childhood together, the girl got jealous of another girl with the MC, so what happened is that she tied up the girl and cut her I think, while telling her, to promise never to see the MC again. The MC eventually found out about it and traumatized.

Now , they are in their teen I think, the mc character wanted revenge and with the help of the victim's little sister, but the failed, of course, somehow the crazy girl manage to turn the table around, to threaten them, as long as the MC stay in love with her, nothing will happen to the victim and her sister.

I lose my title list so hopefully, someone will help thank

Maybe Ijousha no Ai