Jirou Hitoyoshi is charged with secretly listening in on a secret meeting between a senior government scientist and an industrial spy on a bright July day in the 41st year of the Shinka Era. His cover is compromised, however, and the spy exposes himself to be an extraterrestrial in disguise. In the middle of the mayhem, Jirou enlists the help of Kikko Hoshino, a café server and magical girl who is one of many "superhumans" who blend into society and covertly guard mankind from extraterrestrial dangers. Jirou, as a member of the government agency known as the Super Population Research Laboratory, is tasked with both safeguarding superhumans who defend mankind and disposing of those judged too dangerous to live. Kikko is invited to the meeting since she has proved herself to be a worthy ally.