See
http://www.sonyreaderboards.com/foru...hp?f=16&t=3170
It's in regard to other languages, but you probably have to follow the same steps.
If you can figure out which icon on the main screens are for Settings, and press that, the first entry in Settings is usually "General".
On my T1, the Settings icon is on the second page of the main menu, on the lower left side of the screen, with a picture that looks like a toolbox.
Pressing that brings up the Settings screen. General Settings is the first entry on the top of the screen. Does Japanese read right to left? If so, then it would probably be the first column on the right.
Pressing General Settings brings up a sub-menu and Menu Language is the second option down from the top. In a right-left orientation, probably second from the right. If you can get that far, probably any entry you push is going to give you another language, and if you can get to one of the Romance Language ones, you'll have a better chance of figuring out what's what.
You might also want to translate the terms Settings, General Settings, and Menu Language from English to Japanese using one of the online programs and see if you can compare the characters in those words to something showing up on your T2.
Hope this helps a bit.