Sakiko and Masao live alone after her father disappears. Sakiko wants him to grow into a real man, so she looks after him, but Masao's rebellion grows stronger. One day, Sakiko says she wants to introduce her boyfriend, Yoshikazu, to Masao, with the intention of getting married. Masao pours out all his feelings to Sakiko, and seeing how hard she tries to please him, he allows them to have a forbidden encounter, with the promise that it will only be once... This is a full-scale incest drama that vividly depicts the forbidden sexuality of a woman who has given birth and grown older!