Kou comes to a certain city, in search of his older brother Takumi, who ran away from home and disappeared. Thinking it'd be rather difficult to find his older brother, Kou decides not to go back until he finds him... but he ends up finding him immediately. However, when Kou is reunited with Takumi, he had become the head of the Mikuni Detective Agency. Takumi appears to have no intentions to go back home. Kou then decides that if his older brother isn't going to come home, he's going to stay at the Mikuni Detective Agency.