So who killed kirin's sister?

Seriously?
She killed herself. The abuse and trauma she suffered led her to it. It’s right in the beginning of the story.

It’s also right there in the description of the manhwa xD

She committed suicide. Maybe you wanted to ask who raped her first?

Oh yes, I wanted to ask this. I meant who drove her to kill herself.

It was a number of people, but one of the main men who assaulted her ended up dying when he was pushed off the mountain. Another died from being shot by the shotgun. I think the rest were taken care of too

So justice has served them right. Thank you!! (づ￣ ³￣)づ

imo r*pists deserve MORE than death. they deserve slow agonizing pain for years but yea at least they're dead LOL