Their world is a different, one where there were humans and other creatures, living together in harmony. These creatures were what humans referred to as half-beings. They could walk and talk like humans, but retained the features of a animal. A good example are nekos, the human-like creatures with cat ears and tails. The ones above them all are the lunas. They, like nekos, look like humans but keep the ears and tails of a wolf. Like the nekos, they have forgotten about their days as wild animals and prefer to stick to this mostly human form. The ones who wish to go back to that... Well, they usually aren't heard from after their opinion is made public.
A couple were executed years ago because they did this. In the woods, they left a child where nobody could find him. He was raised by foxes, a boy knowing only of the forest and glancing at the world others like him loved so much. One day while in the area near the castle, he finds himself face-to-face with the princess. The two start to walk to one another. They continue to meet like this for days until he asks her to join him for one night in the woods. And she does. Then, everything goes wrong. As soon as they return, he finds himself tossed into the dungeon, accused of trying to kidnap her. Once it is found out that they slept together, he is tortured.
He snaps one day and kills the king himself. In his anger, he proclaims himself king and takes her as his bride (whether she likes it or not). Night after night he forces himself on her, binding her if she happens to struggle. As he lust escalates, he yearns for her more, wanting to turn her so that she could be as lustful as he.
((This is more sexual than anything, really. I would like to give him a harem, or for there to be just one more female. Since I know most don't like it though I kept it down to just the princess.))