Well this is easy to download. I don't think my version of firefox is keen on it though. Need to upgrade. Will let you know
If I find anything similar for more recent versions I'll post in here But I'm useless so if anyone else knows of anything feel free to post it!
uhh im having trouble downloading the language pack... there doesnt seem to be a download button, and when i validate theres an error....
For all those with a more recent version of Firefox (2.0 - 3.0) Here's the correct link for the Japanese add-on