Whenever panties appear on the balcony, it is Rei's secret signal that she is ready for sex. Newly married but sexually frustrated, she feels trapped by her conservative husband. Her desires begin to emerge after Nakata, a single middle-aged man, moves in next door. Rei starts hanging out her underwear behind her husband's back to invite him over, using an air-conditioner repair as an excuse to bring him inside. Their secret affair continues whenever her husband is away, and Rei grows bolder with every encounter.