I'm looking for an anime that I watched a few years ago. It's about another world where there are "old world"-type kingdoms where all the Kings and Queens are chosen by a person who live on a high mountain. The people that are born of that person, are born from pods that grow from a special tree that only grows on that mountain.
Each of these people are assigned to one of the kingdoms before they are born and possess great power. Among their abilities, they can transform into a horse-like creature. The leaders of these kingdoms never age.
The story is about one of these people who can't find the chosen one, so he comes to our world, finds a young girl and takes her back to his world, but they run into trouble trying to get to the kingdom where she is to be Queen.