Miho's stepson Takeshi has always secretly watched her bathe. One day, Miho accidentally catches Takeshi masturbating with her underwear. Confronted on the spot, Takeshi confesses his uncontrollable desire for her and pleads to continue. Though Miho knows it's wrong, she can't resist, and the two begin a secret affair whenever her husband is away. This passionate, forbidden relationship unfolds as their emotions shift and intensify.