Pfft, blackbelt and swords are like bringing knives to a gun fight, it's like my buddy in force recon says "The only unfair fight is the one you lose."
Haha oh well, I'll be 21 in August and although I do love highschool girls, even 17 is too young for me! She is a cute girl though, you should start being extremely protective. Make a weapon room with all sorts of swords and guns mounted on the wall, then make her boyfriends sleep in there and before they go to sleep in a really deep and serious voice say: "Don't touch anything, they're all loaded."