Rin is a family of three with her husband and her husband's stepchild, Akira. Recently, however, my husband has been busy with work and is not at home, so I tend to continue living with Rin and Akira. One day ... When Akira tried to take a bath as usual, Rin was there first ... And without noticing that Akira is watching, Rin begins to masturbate by playing with her crotch.