Although her relationship with her husband isn't bad, Rin has been feeling frustrated lately due to his lack of interest in sex. One day, her sister-in-law Mio comes to visit. The three of them drink together at dinner, but Rin's husband quickly passes out from too much alcohol. With the conversation flowing easily between the two women, the topic naturally turns to intimacy. After hearing Rin's complaints, Mio's gaze toward her shifts, suddenly pushing her down and locking into a deep, passionate kiss. Confused at first, Rin gradually succumbs to these unfamiliar pleasures, stepping into the world of lesbian passion that unfolds before her.