[English/Anglais]
1-First, you need to download (Locale Emulator) : https://xupefei.github.io/Locale-Emulator/

2-After that install Locale Emulator (Tuto under the download button on the website)

3-Next, Right click on the .exe of the game > Locale Emulator > Run in Japanese (Admin)

Easy.

[French/Français]

1-Télécharger Locale Emulator : https://xupefei.github.io/Locale-Emulator/

2-Installer Locale Emulator (Y'a un tuto sur le site)

3-Clique droit sur le .exe du jeux "Mirror Maker.exe" > Locale Emulator > Run in Japanese (Admin)

Easy.