Gangsta.

At twenty, A Wen, directionless and lacking skills, leaves home after an argument with his father, never expecting to return. Twelve years later, he comes back as a man with a criminal record. Fifteen-year-old Li Ming, a gifted student, is constantly bullied by local thugs because of his close friendship with Wang Yu-ting, the girlfriend of the gang leader. When A Wen saves him from the thugs, Li Ming asks him to be his bodyguard, hoping for protection from further bullying.