In the year 311 of the orbital calendar, humanity has migrated to countless colony clusters in space. Akiha Shishido encounters a malevolent artificial intelligence, Leopard, who has been installed on a colony. She is joined by Inter-Colony-Police officer Itsuki Kannagi, taciturn young girl Honoka Kawai and a robot-potato, Imoko “Imo-chan” Shishido.