Rikka Isurugi has spent her whole life learning the ways of the ninja with her grandpa Hyoe, following in the footsteps of her father, the renowned scholar Allen. His efforts have resulted in a collection of cutting-edge drones armed with artificial intelligence and extraordinary technical skills; although Allen intends to develop these drones for civilian use, others have more nefarious objectives. On Rikka's 16th birthday, a paramilitary squad assaults the Isurugi residence in quest of the drone technology, murdering Allen and Hyoe but allowing Rikka to escape with the drones. Months pass, and Rikka is now a regular girl who works as a private detective and shares an apartment with another female, Melissa.