Junko lost her husband about ten years ago, and she has been bringing up Ryouichi, her son, alone since then. One night, when he is asleep, she secretly gives him a blowjob and has sex with him. Junko remarried with a rich guy and a stepdaughter. Ryouichi and her stepsister doesn't get along. One day her son sees her mother having sex with the stepfather. It turns him on. But Ryouichi have something more tricks in his sleeves. An immoral mom and horny stepsister all in one roof.