Kenji, a husband, comes to his wife Kiyoka's parents' house to prepare for the birth of the baby. Kiyoka's older sister Iroha, who divorced Kiyoka's father several years ago, lives there. Since Kiyoka became pregnant, Kenji has been denied sex, and his sexual desire has been building up. He becomes obsessed with Iroha , who has a voluptuous body and exudes erotic pheromones. Unable to resist peeking at Iroha while Iroha is not looking...