Thank you! You are definitely right about the second character but the first is much more complex than what you have written. Although it is stamped very deep and hard to read.
There is no kanji that I am aware of that "perfectly matches" the character on your knife.
It is not uncommon in Japanese knifemaking where a Kanji that is completely out of use, or
does not even exist is used, and read a certain way, as chosen by the owner. Or it is written in such a style
that it dioes not "match" the character as printed on paper or screen.
If that character is stanmped very deep as you say, please run black ink over it to make itn stand out.
Or, put a thin sheet of paper over it and make a soft lead pencil rubbing.
One interpretation could be 久 and 米 arbitrairily put together to be read Kume. If so, it would be KumeMasa.
However, that's not a known name, whereas ShouMasa is an actual existing name.
In either case, that brand is (likely long) out of production.
I am not making guesses here, I am Japanese. I
