In my opinion the birthday dad died was originally his and he has some psychotic tendencies like killing the fish etc and it made everyone around him to be afraid of him and actually blame him for their dad's death so he had a miserable childhood not the main character.Normal timeline main character had a good childhood that's why he can go to the university etc and his evil brother was in shady business living miserable as an adult but since their mother was only caring for the main character he wanted his to get a "taste" of it
He's a psycho. Literal definition. He didn't want him as a brother bcuz of.... incestual tendencies I'd say.
Can someone explain the brothers character to me a bit more? Like.... Why did he turn into a eveil spirit? And why despise yoon sm when yoon was the one who loved him for who he was. Why did he wish yoon was not his little brother. ...