You've had fantasies before, seeing a girl in her bed... hiding from the world... but enjoying herself. Still, she's hiding it in her room even, under the covers. It makes it that much dirty that the whole idea is that she's under the covers, JUST in case someone walks in on her. This is how I'm feeling, hiding under my covers during the day - just so horny that I can't help but masturbate when I have the time. Still though, you never know if someone might walk in on you. It's just so naughty!