Shinya learns that his father-in-law has been hospitalized and decides to move in with his mother-in-law, Rie, not wanting to worry her as she lives alone. Though his actions stem from genuine concern as a dutiful son-in-law, his wife senses his true feelings and realizes Shinya sees Rie as a woman. Their marriage quickly deteriorates, and eventually Shinya leaves home. With the father hospitalized and the wife gone, the barrier between Rie and Shinya rapidly crumbles, leading them into a forbidden relationship.