The implications that he's being forced to rape her is pretty fucked up, but intriguing if your trying to explain the larger system at work here.
He's definitely being forced to rape her. Just looking at the picture you can see that they are chained together by the collar and his hands are shackled behind her back and her feet are shackled behind his back. Plus his face doesn't look like he really want to do it and someone is clearly holding that sword.
I- I'm terribly sorry!This is your first warning.
There's still a use for you after this, after all.Just a knight and a girl alone,
what could be so hard?Finish it quickly!Yes!*Various sobbing sounds*