[Galaxy Note II Q&A, Help & Troubleshooting] yubimusubi:
I grabbed the stock Japanese firmware for the SC-02E here (or you can get it from sammobile):

http://xdaforums.com/showthread.php?t=1996006

The files I added from the firmware were these (sorry long list):

system/fonts/UDGothic-Regular.ttf
system/fonts/UDGothic-Bold.ttf
system/fonts/UDGothic-Italic.ttf
system/fonts/truetypeEmoji.ttf
system/fonts/UDGothic-BoldItalic.ttf
system/lib/libnjaddress_voiceeditor.so
system/lib/libennjubase1gb.so
system/lib/libmazecdict.so
system/lib/libennjubase1gb_voiceeditor.so
system/lib/lib_dic_en_USUK_urldotcom.conf.so
system/lib/libnjubaseidx1_voiceeditor.so
system/lib/libnjname.so
system/lib/lib_dic_morphem_ja_JP_voiceeditor.conf.so
system/lib/libMazecRecJpnDicD.so
system/lib/libnjemoji_voiceeditor.so
system/lib/libnjcon.so
system/lib/libnjaddress.so
system/lib/libiwnn_voiceeditor.so
system/lib/libMazecRecJpnDicB.so
system/lib/libnjexyomi_voiceeditor.so
system/lib/libnjtan.so
system/lib/libnjcon_voiceeditor.so
system/lib/libnjfzk_voiceeditor.so
system/lib/libMazecRecognizer.so
system/lib/lib_dic_en_USUK_emaildotcom.conf.so
system/lib/libnjubase2_voiceeditor.so
system/lib/libkaomoji_tyukyu_voiceeditor.so
system/lib/libennjcon.so
system/lib/libnjubase1.so
system/lib/libEnjemailuri_voiceeditor.so
system/lib/lib_dic_en_xlarge_USUK_voiceeditor.conf.so
system/lib/libnjtan_voiceeditor.so
system/lib/lib_dic_ja_xlarge_JP.conf.so
system/lib/libennjubase2_voiceeditor.so
system/lib/lib_dic_en_xlarge_USUK.conf.so
system/lib/lib_dic_en_USUK.conf.so
system/lib/libMazecJpnDic.so
system/lib/libennjubase2.so
system/lib/libiwnn.so
system/lib/lib_dic_morphem_ja_JP.conf.so
system/lib/libennjubase1_voiceeditor.so
system/lib/libnjfzk.so
system/lib/libnjubase2.so
system/lib/libennjubase3.so
system/lib/libMazecRecJpnDicC.so
system/lib/lib_dic_ja_JP.conf.so
system/lib/libkaomoji_kihon_voiceeditor.so
system/lib/libennjcon_voiceeditor.so
system/lib/libnjname_voiceeditor.so
system/lib/libnjemoji.so
system/lib/libnjexyomi.so
system/lib/lib_dic_ja_JP_voiceeditor.conf.so
system/lib/libkaomoji_kihon.so
system/lib/libnjubaseidx2_voiceeditor.so
system/lib/libennjubase1us_voiceeditor.so
system/lib/libennjyomi.so
system/lib/libennjubase3_voiceeditor.so
system/lib/libennjubase1us.so
system/lib/libMazecRecJpnDicA.so
system/lib/libnjubase1_voiceeditor.so
system/lib/libennjyomi_voiceeditor.so
system/lib/libkaomoji_tyukyu.so
system/lib/lib_dic_en_USUK_voiceeditor.conf.so
system/lib/libEnjemailuri.so
system/VODB/ja_JP/checked
system/VODB/ja_JP/files.txt
system/VODB/ja_JP/ja_JP_jisx0213-lk-text.lite.res
system/VODB/ja_JP/ja_JP.lang
system/VODB/ja_JP/ja_JP_jisx0213-ak-cur.lite.res
system/voiceeditor.prop
system/app/DcmVoiceSearch.apk
system/app/DcmVoiceEditor.apk
system/app/Maruberi.apk
system/app/iWnnIME_T0.apk
system/app/DcmVoiceRecognition.apk
system/app/Mazec.apk

I'm not sure if all of them are actually necessary or not, but that's what got iWNN (called "Samsung Japanese Keypad" in the UI) and MazeC (for handwriting) working on my US (TMobile) Note2. The voice recognition will fail with a SIM card error unless you have a Docomo SIM (so go into the settings and change voice input to Google Voice - I'm not sure how well that works), and I don't think this gets emoji working (it probably wouldn't work anyway outside Japan).

The process to get them was a bit involved. I had to untar the tar file, then run sim2img on the system.img and cache.img... then after mounting both, in the cache partition, there is a file recovery/sec_csc.zip. Most of the files I listed above are in the system partition, but the rest need to be extracted from that zip file. Then you can put them in place with a root file manager or adb.... If that sounds like too much work, maybe I can zip the the files up (not a flashable zip) and post them here.

Besides that, I'm a bit surprised by the lack of integration compared to the built in keyboard, especially with the multiwindow (it doesn't detach like the builtin keyboard). Also, you'll have to switch back to the "Samsung Keyboard" to get the sliding input or decent English handwriting recognition. So, I'm not sure if I actually missed anything and it or maybe that's just how it works.

The theming/colors also won't match what you see in the videos - it's more gray like the default keyboard on US Note2, while it appears to be blue in the youtube videos I found.