Eri and Kiyoshi in their third year of marriage. Although the couple is on good terms, the number of times they have sex is decreasing. Eri felt unsatisfied, but she couldn't beg for the light Kiyoshi, and secretly comforted herself with masturbation. - One day, her brother-in-law Goshi, who often comes to play, sees her masturbation. - Goshi presses for a relationship while affirming to Eri, who desperately deceives, "It's not something to be ashamed of." - Although she thought she shouldn't, Eri, who was defeated by curiosity and Goshi's forcefulness, gradually revealed the desires that she had hidden until now.