Okinawan high schooler Kio Kakazu is at a memorial service for his ancestors when a cat-eared girl named Eris drops out of the sky and calls herself an alien from the planet Catia. Rival agencies and a cult that worships her people all want her found, so Kio takes her in and keeps her hidden, helped by schoolmates Manami Kinjou and Aoi Futaba, who turn out to be working for two of those agencies themselves. This light novel is the source material behind the Cat Planet Cuties manga and anime.