Yumiko's sex drive increases with age, and her husband alone cannot satisfy her. However, a major incident occurs where her husband becomes impotent. In this emergency situation, Yumiko encounters her son Katsu's erect penis as he enters puberty and can't hold back any longer. However, Katsu quickly ejaculates into her mature body. Not satisfied at all, Yumiko uses cleaning fellatio to make him hard again and inserts it into her vagina...
