Tsubaki Kato, Rio's mother and a bisexual woman, divorced and now lives alone with her daughter. Mitsuha Higuchi, Rio's close friend raised by a single parent, initially feels resentment toward Tsubaki but gradually becomes drawn to her warmth and affection. One night, while staying over at Rio's house, Mitsuha is taken aback when Tsubaki boldly steals a kiss. Later that night, realizing Mitsuha's hidden desires, Tsubaki intensifies her advances while her daughter is sleeping...