@Kireato im pretty sure is because Yamashita was pretty scared when he presented himself to Ohma and he said his name really fast ''YamashitaKazuo'' and it kinda sticks to Ohma
So when the Fang uses Martial Arts he uses the royal ''We'' but when he goes to his formless style he uses ''I'', thats interesting. Also if the Beard keeps breaking more fingers is gonna be hard to use the Devil Lance