I find this so fascinating. Years ago I remember reading the fact that most rapes are less about the sex and are about power. I see this being potrayed here.
I usually despise rape, I'm the first to nope out of a fic or comic that depicts that, because it always leaves a bad taste in my mouth. Most writers/artists fail to portray it in the right way so I just leave and never look back but somehow they've got it right.
As we've seen Rian has a slight disconnect from his body, he treats it mostly like a tool that's in his arsenal as a spy except when it comes to sex, and even that feels slightly strange - it feels like an act. A formula a + b = pleasure and co-operation.
What I see Enzo doing is making Rian 'submit' to him, speaking a language he can understand - sex. Saying 'this is no longer yours, it is mine, submit, understand this is where you belong now', that's why Rian is so nonchalant about the noncon/rape sex because in the end its not about the sex.
If the author manages to continue on this vein, in this thought process going forward in the story, I'm going to be sooo happy.
Or maybe I'm just reading too much into it. But I'm enjoying this far more than Red Candy. Then again I really enjoyed Red Mansion and Black Mirror so this is probably the same sort of psychological games happening with our characters.