You might as well

Any illusion that you and Robin might have a future together is now shattered. Meanwhile, Robin is lying forward on the examination table with her face turned to the side and eyes closed, satisfied with her tryst with the father of the girl waiting outside. Her skirt is still hiked up to her waist, while the tiny white panties she's wearing is still pulled to the side, partially covering her puffy pussy lips.

You're heartbroken, but at least you know the truth about Robin. Given the circumstances under which you 2 had met, you guess this was to be expected. Neither of you were going to commit to 1 person, and if you hadn't thought to come surprise Robin, you might have thought she was special.

Nonetheless, your cock can't ignore the sight before you either, so you quietly unzip your pants and pull them down with your boxers. You step up to Robin, still invisible, giving yourself a couple of warm-up strokes, before you reach down to pull her panties out of the way and insert yourself into her recently used pussy. Robin reacts by gasping and gripping the table, although she doesn't open her eyes.

"Couldn't leave, huh?" she half moans, content to feel you inside her. She doesn't even notice that you're a couple inches longer than the former occupant of her pussy as you start to hump her.

"Mmmm, yeah, nice and slow.... I can't believe you're hard again so fast... It's a good thing, I was itching for more..." Robin says sleepily with a smile on her face. Not wanting to alarm her, you continue at the slow but sure pace, enjoying the feeling of her warm pussy walls embracing your cock. You're already excited from watching her just now, and eventually you start to pick up the pace without noticing, fucking her with more vigor. Robin responds to your passion by moaning even louder, louder than before and without thinking about the reception or girl outside, who must be gone by now with her father. It doesn't take long for you to reach climax as you keep fucking Robin faster and harder, and you cum inside her without warning. At first, Robin moans sensually as she feels your warm fluids inside her, before she realizes what is going on and opens her eyes.

"Not inside me!" she gasps, turning over her shoulder. Then, her shock goes into overdrive when she doesn't see the father of the girl outside, or for that matter, anyone at all. "What the-" she says, interrupted by her own involuntarily spasms as she cums too while you hold her down firmly and finish inside of her. She's still trying to get over her own climax when you're done and pull out, and you step back to watch her stare around wildly in shock. She has no idea what's going on, and she sits up on the examination table and spreads her legs, reaching down with a hand to feel inside her pussy. When she withdraws it and raises it to her face, you can see some of your cum on her fingertip. "What the fuck?" she says, looking around again as you teleport away.