A piece is available, so you act like any morally upright lad would. You make sure your girlfriend isn't watching. Yes, she has laid down for a nap to digest that Chinese piece. So party time.

"Come on. Time to put you back in chains."

"Ooo...Are you thinking of taking advantage of me?"

"Now whatever gives you that idea?"

Her response is to point to your pants, which are inadequately hiding your interest.

"Well, anyway, it's back in chains for you."

She makes no problem, putting up her hands to be put in chains, and spreading her legs as the ankle chains are locked on. Now, she is quite at your mercy, a situation she does not seem horrified about.
Using her dry seems a little too unfair, and so you start caressing her, starting with her boobs and switching to her slit. She makes some protests of rather doubtful sincerity, but her excitement mounts, and then she comes.

Now you enter her, your rod entering her quite gently, almost delicately, but she is an experienced lass and in no need of such care. Instead, she shoves herself at you. That is a reaction that sets you off.
For a moment, you rest against her. Then you set to pumping. It does not take long for both of you to climax again.

As you separate and get your clothes back on, you ask "How was that for mistreatment?"