Aki, a second wife, lived a happy life with her husband and their son, Hiroshi. But last year, when her husband went on a business trip for six months, something happened. Without her husband, Aki was left alone with her stepson... Unable to bear the loneliness, Aki made a mistake and spent a night with her son. And what was meant to be a one-time mistake upset her son, and the two of them began to indulge in carnal desires regardless of time or place, and even after his father returned from his business trip, they still passionately desired each other.