Mitsuhiko Okaya, an unremarkable man, was betrayed by his wife and a junior colleague. At work, he was mocked as a useless editor and spiraled into despair, until one day before him appeared a pair of twin high school girls he shouldn't know, yet somehow seemed familiar. The younger twin, Akari, was lively, cheerful, and always teasing him, while the elder twin, Nanako, was shy and clumsy, yet secretly a closet pervert. They were once his students from the cram school where he worked during his student days.