Read To Not Die Manga
Im Dajun is a high school student who gets bullied at school every day. He came across an interview on TV just when he was on the verge of giving up on life. It was with a murderer who killed the classmates that bullied him. Dajun becomes inspired by what he saw and decides to take revenge as well.
His revenge was successful. However, his life steered into an undesired direction. Im Dajun, leaving school, ends up joining a strange Runaway Fam.
The young runaway, Im Dajun, no longer suffers from the bullies at his school. Instead, he now must survive against even more vicious thugs on the streets.