Dumb Luck
WHACK
She suddenly draws her foot back and quickly smashes it right into your fully exposed balls. You're shocked out of lust and reach instinctively for your balls, you cradle them and hunch forward whimpering.
"Ooh that was a really hard one for me even, did you hear the sound it made when my foot met your testicles? Wow, I think I have a new favorite sound."
You look up at her and are immediately entranced by how excited she clearly is, the way she is pulling on her thong gives you a raging hard on and you forget about the aching in your balls.
"Back into position slave," she tells you, addressing you as slave for the first time. You feel proud as you stiffen back into position. Back straight, legs spread wide, cock held out of the way. She smiles at you approvingly as she starts to approach you again, her hips in full swing.