Thanks to your kind inputs, I made a series of editing in files using a combination of HxD Hex Editor and Notepad++ (turned out I had to make a key table for English letters in Shift-JIS Hex values and tune the encoding), I figured I should first edit the game's exe file first (It is a pain already). So I tried playing the items because it looked easy....
I've managed to change (harmlessly) the "Herb" item using the method I mentioned.(Using the Camera because the game always goes fullscreen)
Notice that レスの葉 and Herb have 4 characters
needing 8 Blocks in Hex Editor
the same can't be done with "Torch" or たいまつ because
I tried writing it normally and "inserting it" thus increasing the file size, when this happened:
As FAST6191 mentioned, it is the memory/space issue. The exe file completely changes and is rendered unusable. Notice it stayed itself when I changed "Herb"
I consider this an improvement, since I was trying and failing at changing the "Slime" enemy file.
Whatever this problem is, it is going to be present in EVERY LINE OF CODE FOR THIS GAME. If a solution is figured out and mastered, the translation for this game might become a possibility one day.
I thank you again for your ideas