Tempest:
http://mydramalist.com/2704-tempest
A man wants his son to reclaim the throne of the Ryukyu kingdom (while the Japanese also have their eyes on it), but for various reasons sends his bookish daughter (Nakama Yukie), disguised as a man, to the court instead. This drama has a few supernatural elements, but not enough to say that it belongs in the "fantasy" genre; I felt like it could have been more of that, but this drama was afraid to go all the way... I loved it, though.
I also love the currently airing Gunshi Kanbei, but it doesn't have any supernatural elements. (And there are a bunch of lords, no royalty.)
http://mydramalist.com/8819-gunshi-kanbei
