Playing a Bad Ass K-1 Fighter in A Love to Kill .... Kang Bok-gu (Rain) is a skilled K-1 fighter. However, he has never tried to win a single fight, as he has no desire for the attention that will come with a title. He lives in the same house with Han Da-jung (Kim Sa-rang), who saved him from a fire when they were teenagers. Racked by guilt that she became scarred as a result and knowing her love for him, Bok-gu intends to spend the rest of his life with her, even though he is not in love with her. After years of being estranged from his older brother Kang Min-gu (Kim Young-jae), Bok-gu finally reconciles with him. However, the reunion is short-lived. Min-gu attempts suicide upon learning of the engagement of his ex-girlfriend, Cha Eun-suk (Shin Min-ah).