Yes, this is exactly where I copied and replaced all files provided. I have done this with each update since 1.5, so I'm really not sure why the menus are not translated.
See the picture. Try to delete the files in 1 (** make a backup first!! **). Start ClipStudio Paint. If it CRASH means that it's the right folder.
If not, try to copy the translated files on 2. and restart ClipStudio Paint. ("other" folder usually contains the same japanese resource files as "Japanese" one.)
In the first case the application
loads those files. It must work. If it doesn't work you're probably wrong to copy the files. Or maybe you have a strange lang configuration on your PC.
Remember that in order to copy the distribution files you MUST be an administrator or have administrative rights on the "C \ Program Files" structure. Also try to decompress the distribution into a test folder. Then copy the structure on Celsys one. Surely Windows will ask you for an administrator password.
Good Luck.