The story follows Lee Tang, an ordinary college student, who gets into an argument with a customer during a part-time job at a convenience store at night, unconsciously swings a hammer, and kills him. Suffering from guilt and fear of murder, Lee Tang learns one day that the person he killed was a serial killer and slowly realizes that he has a supernatural ability to identify “bad seeds”. He soon becomes a dark hero who punishes people who committed unethical evils in the past. A cold-blooded, charismatic and persistent detective starts to chase Lee Tang.