The Yuuki and Kirioka families share a close-knit, neighborly bond, nurturing warm relationships in their everyday lives. Amid this setting, Kota struggles with erectile dysfunction and desperately searches for a solution. To his surprise, Satsuki—experienced and confident—offers an unexpected proposal, saying, "Leave it to me." Intrigued and astonished, Kota becomes curious about the kind of treatment she has in mind. Meanwhile, Satsuki's son, Kenji, accidentally discovers Misa masturbating. This incident triggers a forbidden mother-son swap between the two families, spiraling into intense incestuous affairs. Explored through everyday connections and unforeseen events, a web of taboo relationships begins to unfold among the four individuals.