欲負け巨乳妻 ～牝穴は裏取引で捧げられた貢物～

The story centers around Aoyama Mako, a housewife who is frustrated by her husband Keisuke's erectile dysfunction, leading to a lack of intimacy in their marriage. Keisuke's workplace involves international dealings, and he also acts as a host for foreign exchange students. When the company president's wife falls ill, Mako is tasked with taking care of the exchange student, Billy Wilson.

One day, due to a mishap, Mako and Billy end up in the bath together, and Mako becomes intrigued by Billy's well-endowed genitalia. Despite Billy's promiscuous past, he possesses impressive stamina. As they engage in intimate acts, Mako's pent-up sexual desires from her long period of abstinence lead them to cross boundaries.