After her husband was transferred overseas and left the house, stepmother Kogiku began indulging in masturbation out of loneliness. Seeing her like this, her stepsons—having always viewed her as a real mother—felt a deep responsibility to protect her. After extensive discussions between the brothers, they made the decision to engage in an affair with Kogiku. A few years prior, Kogiku had married a man with children, and their family life had been warm and peaceful. But with her husband absent, emptiness began to spread. Sensing her loneliness sincerely, the sons took action to support her. Their relationship with their stepmother weaves together familial bonds and passion, deepening into a new, intimate connection.