I'm looking for a manga which I read long time ago. The manga is completed but the its light novel is not. The main character is a cunning prince and his adversary is a war princess of the opposite country. I cannot remember the story clearly but the prince is captured by the princess but he is released because of his intelligence. And at the end of the manga, the prince won the war because he is outsmart the war princess. Other detail is the war princess is the third princess, I believe the first princess is very politics.