Imagine masturbating (guy) while straddling over your wife (or S.O.). SHe is reaching down and playing with herself as well. As you continue to rub your member on her tits, she asked you to cum on them. When you follow on this request with a question "does that turn you on, seeing me cum on you"?....she throws in the ultimate trump card. "as long as you clean it up after" (meaning lick it off her tit's).
Guys - Would you? Could you?
Girls - Would you enjoy watching that?
Guys - Would you? Could you?
Girls - Would you enjoy watching that?