Planetarian: Hoshi no Hito, an adaptation of Key's visual novel, mixes the original work's tale with an extension that extends the storyline with information from the Hoshi no Hito light-novel sequel. After most of the globe has been ravaged by nuclear and biological warfare, a teenage scavenger or "Junker" roaming a confined and abandoned city discovers a service robot still diligently awaiting guests in a department store's rooftop planetarium. Against his better judgment, he assists the robot in repairing the planetarium's projector, a choice that will transform both of their lives.