
Its not clear for me too. But we will find out in later chapters i am sure
Here a spoiler from Haribo twitter
https://mobile.twitter.com/hamgi5492/status/790763720435568641

The country seems sooooo scary to live in.
Dont they punish rapes and bulling by law?

concerning bullying, schools generally ignore it since otherwise it will lower their reputation. it is technically punishable by law (i think...?) but the parents of both sides will generally try to negotiate with each other, and afterwards the bullying will get worse since it means that the person they were bullying told on them. about raping... in korea it seems that people think its shameful to get raped and wont tell the police about the case. combine that with bullying, it becomes much harder to even detect that theres a problem in the first case let alone punishing it. also i think koreas a slightly misogynistic country and therefore slightly lenient on rapists as well.

I think the bullied kid wanted to die and the poor main character wanted to live, so maybe that's why he got his shot. Also, maybe to right wrongs. Clearly, the bullied kid had a great injustice done against him (although we don't know the whole backstory), and maybe giving this kid a chance at a family and comfortable life and education (all things he wanted and didnt' have) also comes with correcting the evil that led to bullied kid's suicide.
But I still wanna see the brother die. Die horribly.
But I don' understand if the guy who killed himself was raped by his twin or by the guy who has just show up. Anyway I hope that he can be avenged, the first scene when he cries and wears his trousers really hurt my heart ╥﹏╥