Isekai anime with neveraging Kings and Queens, and kingdom's people born from a tree on a mountain

Question

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.

Answer 1

This is The Twelve Kingdoms (十二国記 or 'Jūni Kokuki', 2002).

One of the major stories of the series centers around a red-haired girl named Youko Nakajima from Japan who is suddenly transported to the world of the Twelve Kingdoms and searches for her destiny. However, neither the series nor the anime concentrates solely on Youko and they do tell stories of other characters. The anime uses Youko as a framing device for telling other stories while the novels do not.

Each of the Twelve Kingdoms has a monarch and a Kirin, a mythological beast who first selects and then serves the monarch of his or her kingdom and can assume human form. Though only a few rulers and Kirin are in the main focus of the story, many are encountered in the series and play a significant role.