The younger brother in the movie was really lucky to come to his brother and sister-in-law's house when his brother was away on a business trip, leaving only his sister-in-law at home. It's true that fire near straw will eventually burn, the time without her husband by her side made Suzuki unable to control her desires, sudden arousal like any other married woman. This made her feel very restless, uncomfortable and had to find a way to free herself. Of course, in a small house with only two people, her husband's erotic and provocative actions to help her achieve that desire were understandable.