The Black Belt may seem weak at first, but when you get him to level 10... watch his attack strength sky rocket! The Black Belt's DAMAGE rating is always equal to double his level, unless he has a weapon equipped. So basically, don't equip any weapons on him. Same goes for his defence. His ABSORB [the defence level] is always equal to his level unless he has armor equipped. So when you get him to level 50, his ABSORB will be 50, which is pretty good, considering the highest a Knight can get is 74, so the Black Belt/Master is the best character to have. He requires no armor or weapons. You can test this yourself, Get a Master at L50, and a Knight at L50 and the Knight equipped with the Masamune. Cast FAST on them both, or not. The Master will do far more damage than your Knight, I've checked this myself.