Momo Aoki, a school teacher and swimming club advisor, gradually ends up in a relationship where she allows her body to be taken by Yui Yuki, a former student who quit as an athlete due to an injury. Momo has a fiancé named Ayaka Kagawa, who is a colleague, but she cannot break off her relationship with Yui. Every time Yui's semen is ejaculated inside her, an unknown pleasure assaults her, and her trained beautiful body gradually drifts away from her fiancé…