Since learning that her stepmother, Nana, is secretly masturbating in the bath, Kouta is a son who can't help but peek at him, even though he thinks it's a bad thing. One day, Kota, who was cleaning the bath with Nana, accidentally pours water on Nana from a hose. Kouta panicked for a moment, but when he looked closely, Nana's braless breasts became visible, having been soaked wet... Finally, Kouta can no longer contain her excitement, and as she instinctively pushes Nana down...