Ten years after marrying her childhood friend Hiroshi, Miki feels him growing cold and spending every night out drinking. Their sex life dwindles despite her attempts to tempt him, leaving her painfully lonely. Her only emotional support is Toru, the father-in-law next door who was once her teacher and has always treated her kindly. Old romantic feelings return, and Miki begins subtly seducing him before finally gathering the courage to enter his bedroom.