We follow Kazuki Kurusu, a criminal contractor/coordinator who lives with his best friend, Rei Suwa, a professional assassin who was raised from childhood to be a contract killer. Kazuki is outgoing and loves gambling and women, while Rei is a man of few words who spends his free time playing video games. One day, the two friends end up looking after Miri Unasaka, a four-year-old girl whose father is a mob boss, after Miri accidentally gets into a hotel shootout while searching for her father.
After learning that his daughter was being physically abused by her boyfriend Nobuto, Tetsuo Tosu decides to leave his job as a wage earner to investigate the boy's past further. Upon discovering that Nobuto is part of organized crime and has a history of extortion and murder of his ex-girlfriends, Tetsuo is overcome by anger and fear of losing his daughter and ends up killing the boy. With the help of his wife, Tetsuo dumps the body and decides to pretend that nothing happened. However, Nobuto's criminal organization soon begins investigating his sudden disappearance, leaving Tetsuo and his wife to deal with the consequences of their actions while trying to protect their daughter.