This mod adds ability to make custom translations.
Download translation that you like and place it in Documents/Primitier/Localizations if directory doesn't exist create it or run the mod
A buttons will appear along with localization name. Choose yours by pressing Next and select it with Select button
Then apply it by switching to Japanese (or English) and back
Congratulations! Now you have custom language in Primitier
Here is the list of localizations that exist for this mod