While his mother, Tsubaki, was preparing breakfast, her son woke up in pain with an abnormally swollen abdomen. Recently, Tsubaki's husband has not been paying her any attention, so she has had to make do with masturbating every day. Just imagining her son's morning erection makes her crotch tingle, and she plays with her aroused crotch and indulges in morning masturbation... The next morning, her son, who accidentally saw his mother masturbating yesterday, confesses that his morning erection is because his mother's body is plump and erotic... The two of them start lusting for each other's bodies early in the morning and make love...