Set in the year 311 of the Orbital Calendar, when humanity has settled across countless orbital colonies, the story follows Akiha Shishidou, a girl from one of those colonies. She encounters a malevolent artificial intelligence called Leopard, which has been installed on her colony. Akiha is joined by Inter‑Colony Police officer Itsuki Kannagi, the quiet young girl Honoka Kawai, and a robot named Imoko “Imo‑chan” Shishidou.