Nanako is a mother living alone with her son. One day, she is forced into a sexual encounter against her will. Though reluctant, she eventually gives in and submits her body. Returning home during the act, her son is shocked to see his mother and confesses he watched everything. He then pleads with her to teach him about a woman's body. Troubled but deciding it as part of sex education, Nanako agrees to take him in. The mother and son's relationship begins to transform into something new.