In this world, there are Hummingbirds, humans with a special constitution that allows them to improve their abilities from the bodily fluids of others, and Lilies, whose bodily fluids give them special powers. After a series of incidents in which Hummingbirds target Lilies, the government has tightened its control over Hummingbirds, and the police are wary of them.

Meanwhile, Detective Torazaki, whose partners have always run away from him due to his reckless investigations, is assigned to the X Division, a group of problem children, in order to keep his hopes of continuing as a detective alive, and he teams up with Detective Tatsumi, who has a Hummingbird constitution.

Torazaki rebels against Tatsumi, who always does research without using his feet, but he begins to acknowledge him a little as Tatsumi produces results through information-based investigations. However, when Tatsumi is exposed to the victim's body odor, Torazaki is pushed down by him, and it is discovered that he has a Lily constitution...!?