Denial

"Mmm I can see you're close. Are you going to cum for me?" You mumble a yes from under Megan's ass. "Ooh I bet you can't wait to release your seed for my sexy foot. Beg me to finish you." Your sister moves off of your face to allow you to talk.

"Please Heather finish me off. I want nothing more than to cum for your sexy foot." The humiliation you felt actually made the situation even hotter for you.

"Hmm I don't know that didn't sound convincing enough. I know you can try harder."

"You and Megan have utterly dominated me physically and sexually. As a sign of submission to you I would like you to finish me off like the pathetic bitch I am." Here you were looking up at your sister's ass, begging her friend to stroke your dick with her foot. You were truly their pathetic bitch.

"Well that was much better, but the answer is still no." You heard her giggle sadistically as she removed her foot and walked away to her seat, leaving you excruciatingly close to orgasm.