Newlywed Ryo is forced to live alone with her mother-in-law, Sayoko, while her husband is away for work. The two have been living together affectionately, but Sayoko's hidden feelings for Ryo grow stronger each day. One night, overwhelmed by loneliness, Ryo begins masturbating in her bedroom. Noticing this, Sayoko also starts pleasuring herself. Later that night, unable to contain her desires any longer, Sayoko turns her emotions toward Ryo.