The centaur girl really has no reason to want to marry a human. I mean, it would be no different than F'ing a horse. Her lady parts are on the back end. Getting mounted by a large horse body (with a large horse C*&K) should be part of her instincts.
On the other hand, I can perhaps see the...
Everyone should realize by now that these two will not have sex in this manga... at least, not until the last chapter or two. Until then, they are just going to keep messing around and MC is going to continue getting off at the slightest touch.
I feel like the emotional depth of these characters is paper thin. There is no sense of grief, fear, or anger... it just jumps from one thing to the next and keeps the "plot" moving. Also, Grace just decides to trust him out of nowhere and even seems to have a crush on him now. There just...