Read it again, the captain personally trained him.
Also thats a pretty small katana so it wouldnt get in the way, the fact its double edged also helps with stabbing which an assassin is more likely to do.
@gaigous I thought you guys were arguing weather she could have won it, not if there is a way to counter it with any kind of magic. In which case the most obvious choice is also having creation magic and sending your own soldiers, or using invisibility magic to send a single guy to destroy the...
To be fair that's a pretty lazy shooting range, you could have it be narrow so they can't dodge and have shooting slits on the walls and ceiling for skeletons to support the shooting. Also if she had different powers I imagine the MC would have to come up with a different dungeon, so it's...