For centuries, the deadly arts have been perfected by Masters, and Five Great Families hold the greatest power and influence. Hikaru Gero, an heir to the Gero family, lives in the underworld as an elite assassin. When his sister is pressured to produce an heir, Hikaru asks Mei Kinosaki, a brilliant marriage swindler, to find him a bride. The most challenging mission of his life begins!

The corrupt pure-love story revolves around Kasuga Takao, a bookish boy who loves the poems of Charles Baudelaire (the original author of the poetry collection "Les Fleurs du mal" or "Flowers of Evil"). One day after school, he discovers and steals the gym clothes of Saeki Nanako, the girl he has a crush on. However, he learns that Nakamura Sawa, a girl he loathes, happens to catch him in the act. Nakamura blackmails Kasuga into a contract, or else she will reveal his secret.