Cuckold slave
Maybe it is the thought of her naked and exposed? Is that it, is it thinking about how sexy she is and only you get to see her fully exposed? Look at how her pussy is just open and waiting. You must want to climb on top of her and make her moan your name as you bring her to ecstasy..
Go ahead and strip naked and start stroking that dick slowly while you imagine that is your girl naked and waiting to be fucked.
No? Any real man wouldn't hesitate to bury their dick deep inside her. Any real man would throw her around and use her as their little sex slave without thinking twice! Making her pleasure them until they are fully satisfied and ready to blow their load any where on or in her they see fit.
WAIT.. did I just see you speed up your stroking? Did those last sentences excite you? The thought of a real man coming in and using your precious sweet heart in front of you excites you?
Slow that stroking down as we explore this idea further!