OKay the translation (official files) work fine, however if you wish to have your settings and tools and what not , working with this TRANSLATION you need to copy your user Celsys folder ("C:\Users\your name\Documents\CELSYS") to user Celsys_EN folder ("C:\Users\your name\Documents\CELSYS_EN").
Serial from japanese version does not work with eng version.
This i s one possible solution, there may be other ways too, please share them.
1.install jap version
2.copy eng translation files (taken from official eng version)
to jap version ("C:\Program Files\CELSYS\CLIP STUDIO\CLIP STUDIO PAINT\resource\other")
3.(optional) copy the user folders (explained above) if you wish to have your stuff transferred.
I tried to delete the EN user folder but it keeps regenerating, so....