When you're hanging out with friends at home or drinking, it's common to fall asleep right there, right? In the middle of such a nap, girls straddle the guy! It's a happy thing for the guy, but it's a little awkward with someone sleeping next to him. But it feels good, so he just accepts it. There's a thrill in suppressing your voice so the person next to you doesn't notice, and somehow it gets you more excited than usual, and it seems like this kind of sex will become a habit!