The guys you see in the video are not actually ninjas.
biggrin heart But I know what they are! They're practitioners of
Parkour, or Free Running.
Parkour originated in France, strangely enough, so French is a great nationality switch up if you don't go with Chinese (Chinese = Awesome). The idea behind Parkour is beautiful and efficient movement, but it's taken up by a lot of dumb teenagers/college kids because it looks cool instead.
People that are hardcore with Parkour have to spend a lot of time practicing, and a lot of them have jobs in the movie industry as actors/stuntmen (AKA, the guys you see the hero beating the crap out of in a two second alley scene) for practicality reasons. Being a movie stuntman would be a solid career choice. If you wanted to have him doing some petty crime on the side (burglary, mugging) I think you could work it out. He should probably have some experience as a kid (and mabye on into adult life) with ballet or gymnastics. Ballet could be all kinds of fun.
I'd advise you to beef up in the history and technical terms involved in Parkour, like "Roulade" and "Saut de Détente".
Raurhund really did have some excellent suggestions. Remember, the goal of roleplaying isn't to "win" or have the coolest character. Having a weaker character that may allow others to have the one-up on you is much more admired than a character who could basically take on anyone.