Suddenly I realized I can just do a mockup first instead of editing the sprites in the game practically. (LOL I think I'm not clever at all)
Although I gained a little experience in the tool I found.
EDIT: Tried to make letters used for the
L/R button descriptions looked more "heavier" and more similar to the original Japanese text.

It's based on Silvuh's work.
Ouch, forgot to edit that "i".
Forgot to say these heavier upper case letters can be found in the game ROM.