When her father-in-law unexpectedly shows up to wash her back, Hikaru stares at him with a mix of confusion and embarrassment. This quiet, intellectual man who usually spends his time on the computer has never acted this way before. Before she can even think of a gentle way to refuse, Hikaru finds herself cornered at the edge of the bathtub. As her father-in-law embraces her with a calm, tender expression and soothing voice, she realizes her happy married life is over. In a two-family household where her husband is often absent, a forbidden relationship begins to form, distorting the bonds of family. A story of unexpected desire and familial conflict unfolding from the most ordinary of daily moments.