Holding strictly to his family's creed, Kou Ichinomiya has never once, in his life of privilege, owed anything to anyone – that is, until a self-proclaimed Venusian named Nino saves him from drowning in the wake of a dire accident involving Kou's pants. Eternally indebted to the supposed extraterrestrial, Kou moves into her little community under the bridge along the Arakawa river. Ripped from his life of luxury and success, the young Tokyo U graduate now must adjust to his well-appointed hovel, strange new neighbors, and peculiar lover, Nino.