I can have a go at a hand-done translation of any parts of all of the manual if you wish. My Japanese skills are a bit rusty (intermediate level) but practice is good (even if I may hit a few odd technical terms to throw me should be better than Google Translate). I have done a quickish pass of the first 14 pages of the manual (in full), although I imagine a lot of that info is the least important (I did it all for practice really).
I can do the full thing or prioritise any pages while I finish off the rest. Just let me know. If it goes wel I can technically do this to assist any other devs that need translation work done on a similar scale. Apologies for the new username but my original account is locked to a defunct email address and don't know who to contact to try and retrieve it. (And I have been out of the scene for many years anyway)