Hi Mathis,
To install Japanese locale do the following:
1) Untar the Japanese Language Package (desktoppackage.tar)into a directory (/opt/desktoppackage).
#tar -xvf <Package_name>
2) Do a pkgadd to install the Japanese language and follow the instructions thereafter.
#pkgadd -d . SUNWwtdjp
3) Restart both the Portal Server and Gateway.
To check the Locale:
1) Goto Desktop Servlet and User Information Channel.
2) Click edit and scroll down to Locale Information. You must see the Japanese language included here.
3) Select Japanese locale and click "Finish" button.
4) Log out and return to desktop.
This must help you out in configuring Japanese Locale.
Cheers,
raj_slash.