Five years into her marriage, Shizuko is having an affair with her childhood friend Ken, whom she met again at a class reunion. After they've had sex a few times, Ken becomes interested in Shizuko's big ass, but Shizuko stubbornly refuses anal sex. One day, her classmate Fujiko finds out about their affair. Similarly frustrated, Fujiko calls Ken over and seduces Shizuko with her impressive anal... The relationship between the three, which has become a quagmire, comes to a tragic conclusion on September 9th, the day of the Chrysanthemum Festival.