My girlfriend's name is Harumi, and we've been together for half a year now. Her mother, Mio, is a single mother who raised her daughter on her own. She's good-looking, responsible, and carries herself with a mature charm. However, behind Harumi's back, I've also started a sexual relationship with her mother. We both know it's wrong, but whenever we're alone together, our bodies betray us, inevitably grinding our genitals against each other.