The girls falling on the floor.

In a moment of unexpected clumsiness and with a loud thud, both girls fall to the floor. This isn't like the the threesomes you've seen in porn or even in movies. This is awkward and clumsy. But it's also amazing.

And the girls laugh. Your girlfriend and her best friend are now both on their backs, practically rolling on the floor laughing heartily. Katie's half-nude body and Samantha's totally nude body, are something to behold as the two girls try to control themselves. They're having so much fun.

This is also the first chance you've really gotten to see the trim curly red bush between Samantha's legs. It looks glorious and you can't wait to be there.

And it seems like Katie feels the same way. As the laughing calms, you notice, and clearly so does she, that the girls have fallen in a way that they're positioned head to foot. You see it in her eyes. Katie gets a look at Sam's lovely red pussy, and her desire overtakes her. Her laughter subsides but her smile does not, as she climbs on top of her best friend, positioning herself to 69 her.

You hear Sam say "Hello!" as if she's surprised that her friend is being this bold, and scoot herself up into a semi-sitting position.

Her face is now inches from Katie's underwear-clad ass. And Samantha shakes her head, as if she's telling herself that this situation cannot remain.

These two are so unbelievably playful. You wonder if any of it is for the benefit of your viewing pleasure. If it is, it's working. Your cock is in your hand. But you're trying not to stroke it too much. The last thing you want to do is finish before you get started.

Samantha pulls Katie's panties down off her hips, as far as she can get them, which is more or less just to the tops of her knees. And suddenly she's face to face with her best friend's plump ass and moist twat.

What she does next shocks you and it shocks Katie. You've been sleeping with Katie for 6 years and you know the things that she's into and the things she's not. Although as it turns out, moments of unexpected horniness can open up your girlfriend's mind a bit. Not that you didn't know that about Katie, but still...