A housewife lives with her husband in Tokyo. One day, her nephew Kouki comes to Tokyo from her husband's family home to take an exam. The couple welcomes her nephew, who wants to stay with them in their boarding house in preparation for the exam. The busty housewife is kind and caring, but she's not good at saying no. The virgin exam candidate, who is in the mood for sex, keeps casting inappropriate glances at the voluptuous curves of his "Tokyo aunt." Then, a few days later, on a night when her husband is away at work, the forbidden first-time sex occurs...!