Satoshi, a university student, is in danger of not being able to advance to the next grade due to his habit of skipping classes. Worried about Satoshi, his mother asks his younger sister Chieri, who lives in Tokyo, to keep an eye on him. Satoshi is confused by the sudden start of living with his aunt. He is living like a prison, and can barely masturbate...To top it all off, he accidentally sees Chieri's ripe naked body! Satoshi is at an age where he wants to have sex, and he can't control his pent-up sexual desire...