Japanese?
Wouldn't work, historically. An authentic Japanese katana would be absolutely worthless against European metal armors. You would have a higher chance of shattering the blade on your katana than you would seriously hurting your plated opponent. The Japanese had horribly low quality steel, and so to make a blade that could hold an edge required the steel to be "folded" over itself. Thus, authentic katanas are quite brittle. They aren't the "super sword" so many people claim them to be.
Then there's the differences in armor. In Japan, only the wealthy (such as Samurai) could afford armor. Armor was not made of steel generally, as it would be too brittle to function properly as armor due to its low quality. Most warriors then tended to not wear any considerable amount of armor. Most were armed with "peasant weapons;" farm tools that were adapted to war, such as the kama.
If you were employed in the service of a lord, you probably weren't give anything other than your wages and orders. Lords might take it upon themselves to train some of their peasant serfs as archers, and would provide them with simple bows or whatnot, but an organized, professional army was incredibly rare in Japan as far as my understanding goes.