I am King.

Actually this is one of the stories I wrote when I was ten. It is Korean.
A shaman and a prince. Status divides them. Yeon and Prince Geuma. She helps him discover a conspiracy which is overtaken by the arrival of another person claiming to be the real crown prince. He is given the throne after the king suddenly dies and no one is suspicious. He plots against Geuma and orders for them to be put in exile. They join a Fraternity and can soon beat the greatest assassin of their time. they come back for revenge.
His illegitimate brother took the throne and now that illegitimate son will meet his owner in the battle field.
FORGIVE ME IF IT SOUNDS CHILDISH. pictures aren't mine It is fiction so it shouldn't relate to actual happenings. If found it is purely coincidental.