"Minimum" - a special inborn power found in a limited number of human beings, known as "minimum holders." In Yokohama, the detective team Hamatora, formed by two minimum holders named Nice and Murasaki, comes across information connected to a serial killer being pursued by their old friend Art. It turns out all the victims are minimum holders like them. Unwillingly at first, the two detectives become involved in the investigation.
Kou is searching for his older brother Takumi, who left home and has gone missing in the city. Worried that he's in trouble, Kou decides not to go home until he's found him, only to find him all too easily. Takumi, it turns out, has become head of the Mikuni Detective Agency, and has no intention of going back home. Kou decides that if he can't make Takumi return, then he'll join the agency himself.