Celcom Malaysia has released 188.8.131.526 on Thursday for the BlackBerry Storm2 9520.
member yhamaie says that the "Japanese Input option can be invoked" with this release.
Even if this is not your carrier, just be sure to delete the Vendor file and you shouldn't have any problems loading this OS to your device.
Thanks for the tip.
9520 users give us your take on this build. I'm sure some hybrid builders will start to post some new threads in the forums as well.