@JavelinJoe
As long as they're not up against heavily armored enemies unless it's enhanced / buffed /magicked up to hell, sure, a katana could be #1 for ones who know about it.
If they're up against that type of enemies, and it's not buffed in any way, and the user is not buffed in any way, well...
If they still succeed by slashing, it's either over-pride or legitimate falsification.
That being said, if the MC ever gets ahold of some quite legendary 'native' swords, they tend to be rather OP as well. But those swords are either never mentioned, already have owners, break in the combat to get them or when the MC actually gets one, they're already rather OP (if they get them early on, they tend to be transformable into female humanoids)
But katanas on the other hand. Noone tends to be able to or want to use them. Meaning they tend to be on sale for cheap if the MC finds them that way.