You are my step-son and you wake up naked and tied to the bed to find me straddling you. I tell you that I know you've been fucking your girlfriend, and that you won't be fucking her anymore. I tell you that I'm going to ride your cock while you're tied up, and you don't have a choice. I slide my pussy down on your cock and start fucking you. I'm loud, so my husband/your step-dad walks in to see what's going on. I nonchalantly reveal to you both what my plans are. I caught you and punished you by making you fuck me. As part of the punishment, you will spend the rest of your life as my sex slave, and will serve my every sexual whim and desire. you have no choice whatsoever. I make it clear that I am the only woman you are allowed to be with, or even think about sexually from now on. I tell step-Dad that since I have you now, I have no more use for him and am divorcing him.