Start Grinding

Your hand starts to brush against her ass. Slowly, but surely.

You close in behind her, poking her ever so slightly with your erection. Arrhythmically at first, just to see how or if she would react to you.

She does not react.

You take this as a sign. You start to rub against her ass further, and out of instinct you grab her hips. Driven by this animal-like instinct you start to grind on her ass, faster and faster. Then, you notice that she's starting to push back on your dick. The two of you start to figure out a rhythm to grind your dick against her ass.

You lean in closer to her. You can hear start breathe more heavily and moan slightly, as you two begin to gradually pick up the pace of the grind.