Set in a cyberpunk version of Tokyo. Tsukasa recently joined the organization “Project Nightingale.” The goal of this organization is to prevent crime due to the lack of authority in the city. They urged people of any age to come and join in order to protect their community against danger. All members are supposed to keep their identities secret, even to their friends and family, so most go by code names, Tsukasa’s being St4r (pronounced S-T-four-R) (yes he did pick it out himself)