I have the HP Journada 720. I have only attempted Japanese input with JWPce. Until I got SuperMemo recently, JWPce was the only program I used it for as I bought an old Journada cheaply on eBay expressly for that program.
I expect input will only be possible with a program like JWPce which has it's own input system. Although Japanese can be viewed in Pocket Word and such as there is no problem copying over unicode fonts such as MS Mincho from your desktop machine and using them in applications, including JWPce and SM, of course.
To create Q&A files on the CE machine itself would require you to input into something like JWPce and copy and paste to SM I expect. However, I'd always planned on preparing Q&A "offline" on the desktop and importing, which is what I did with RTK1 Q&A file.
I expect input will only be possible with a program like JWPce which has it's own input system. Although Japanese can be viewed in Pocket Word and such as there is no problem copying over unicode fonts such as MS Mincho from your desktop machine and using them in applications, including JWPce and SM, of course.
To create Q&A files on the CE machine itself would require you to input into something like JWPce and copy and paste to SM I expect. However, I'd always planned on preparing Q&A "offline" on the desktop and importing, which is what I did with RTK1 Q&A file.