Exposed to severe domestic violence as a child, 18-year-old Kim Gwangun has come to view the entire world as hostile. He is armed with an excessively sensitive and violent self-defense mechanism, often reacting to light kindness or small provocations with his fists first. After dropping out of school and being driven onto the streets, he became known as a 'mad dog' among delinquent peers, always fighting to the bitter end. To survive, he took a job as a delivery rider for a run-down Chinese restaurant that provides room and board. Even while continuing his rough delivery work with bruised knuckles, he remains filled with deep-seated deficiencies and wounds, longing for salvation and warmth while unable to fully lean on anyone.