During their trip to the hot spring resort, engaged couple Natsumi finds that one of the maids at the inn bears a striking resemblance to her old boyfriend. Upon learning his name, she discovers he is actually the son she gave up for adoption 22 years ago. Initially intending to leave the inn after finding out about their connection, they decide to stay another night. Despite not being the biological mother, Natsumi can't help but feel affection towards her son and longs to touch him. As they share a bath together, the forbidden temptation becomes too much for them to resist, leading to a passionate encounter that crosses boundaries.
