Eri and Kiyoshi have been married for three years. Although the couple's relationship is good, the number of times they have sex is decreasing. Eri felt unsatisfactory, but she couldn't even ask Kiyoshi, who was indifferent, and secretly comforted herself with masturbation. One day, my brother-in-law Takeshi who often comes to play sees masturbation. Takeshi presses for a relationship while affirming Eri, who desperately tries to deceive him, saying, "It's nothing to be embarrassed about." Even though she thinks it's wrong, Eri loses to her curiosity and Takeshi's aggressiveness, and gradually reveals her hidden desires.