Minoru ends up staying at his older brother's house due to work. Although the couple has no children, Minoru is deeply attracted to his alluring sister-in-law, and secretly spying on her has become his obsession. Watching her intimate moments with his brother, her bathing rituals, the fleeting glimpses as she changes clothes—every moment through his eyes is intensely stimulating. But the story takes a suggestive turn when he realizes his actions have already been noticed by the married couple.