Yutaka Takenouchi is Nishijima Sho, a henchman for Kazuma Ryuichiro, the president of a successful corporation but also, unknown to the public, a mafia boss! However, what the mafia group doesn't know is that Nishijima Sho is actually undercover police detective Kaneyama Takumi. He enters the underworld (the mafia) under the orders of his boss, Detective Isaki Yoshihiko and also because his father was killed in South Korea, which he believes was the work of the mafia.
One day, Sho and his friend go to a bar and find a Korean woman being harrassed. He helps her out. The woman is Choi Yoo-na (Choi Ji-woo), a woman who comes to Japan with her sister in search of their father, who went to Japan and never came back. Yoo-na also seems to draw the unwanted attention of Kim Young-jae, a Korean underboss of Kazuma's mafia group summoned to Japan from Korea for "work."
Also in the scene are Kazuma Ryugo (Mokomichi Hayami), Ryuichiro's son who is set to inherit the corporation (and the mafia), Kazuma Kotomi (Yui Ichikawa), Ryuichiro's daughter who likes Sho (but the love is unrequited), and his Korean aide/secretary for business (and mafia) affairs, Song Gyu-hwan.