While his father is posted abroad, the protagonist temporarily stays with a colleague's family. He wanted to live alone, but sharing a home with the colleague's sultry wife Yuri sends his masturbation frequency soaring. One day he catches blindfolded Yuri having forbidden sex with an older neighbor. As he strokes while watching, the man unexpectedly waves him over to join. Knowing it is wrong but believing the chance will never return, he decides to take Yuri too.