Reo Katsuragi, a lonely life-long professional boxer, lives in Kabukicho, Shinjuku. Although he is talented, he spends days without being able to have a "meaning of living"-One day, Leo, who lost KO in a match against a lower-ranking opponent who cannot lose, found out that he had a terminal illness after the match.

Leo who is in despair meets a girl, Monica, and is involved in a powerful incident that happens in the underground world!