Responses
http://www.mangago.me/read-manga/trace_of_witch/
Try this, it has that mediaval-fantasy setting you're looking for and it's a yaoi.
beta
Ergh I wish I could have been able to get into the story more like everyone else around here but man I dunno. I love the art style and am a sucker for this type of medieval-fantasy setting with yaoi but I couldn't really get into the story... (If anyone else knows a good yaoi with this setting feel free to share, I feel like there aren't enough of those.)