If you mean Japanese text entry, to my knowledge, such functionality is not available, except if you buy a Bold 9000 from NTT DoCoMo in Japan. And before you ask, no, the DoCoMo Bold 9000 OS cannot be installed in your 8520.
For the 8520, Japanese text display should work out of the box. If it doesn't you don't need to reinstall the OS, just simply add the Japanese language option.
9630 #4 < 9630 #3 < 9630 #2 < 9630 < 9530 (returned) < 8703 < 7250