Takeshi and Daisuke are two close friends who have been playing together since they were young. Recently, the sexual relationships of both families have been declining, with a lack of desire for intimacy making their marriages stagnant. Faced with this situation, Daisuke suggested to Takeshi... to swap wives. During a gathering of the two families, Takeshi informed Sakura about Daisuke's proposal. Sakura was hesitant at first, but after being convinced by Takeshi, she agreed. So Takeshi and Yuna proceeded first, while Sakura and Daisuke watched. Watching her husband have sex with another woman right in front of her eyes, without using a condom, and ejaculating directly into Yuna's uterus! Moreover, Daisuke took out his penis and masturbated in front of her. Seeing another man's penis made her even more aroused, her panties had been wet without her realizing it. And after they took a shower, she went with Daisuke to the bedroom of the two couples and had sex right there. After this incident, Sakura was no longer shy as before. All four of them always felt comfortable being naked at home, playing cards and playing the "guess the penis" game with each other, having sex whenever they wanted. The bond between the couples seemed to be getting closer...