I know this little set is implying the girl is getting it on with an unseen dude. Probably meant to be the one viewing the image like most eroge CG's.

Coming back to this after a few years however I am seeing a different and even more pervy scene in my mind.

Sitting alone in some woods close to her home reading romance novels she starts reading through a hot and steamy sex scene. Getting turned on herself she starts stripping down and masturbating imagining the guy from the story is ravishing her against the trees letting out all her wild fantasies out of sight from the world.