A fluff note: I think Arnis De Mano was a Filipino martial art whose practice was forbidden when the Japanese occupied the Philippines. So you would need a good backstory reason for why a pureblood Japanese would learn that particular martial art. I'm not saying nix it - but address why he knows it. Maybe his sensei was an expatriate Filipino who had trouble getting students to learn his disreputable style, and that was part of why the Yaks went out of their way to antagonize him.
Actually from a fluff p.o.v. it makes sense, as he is an ork. With the Philipines being where the Japanese sent their ork and troll populations (don't remember the exact island name), he could have been one of the survivors of that time or the son of a survivor who taught him what little they knew.
