CABs here were tested on clean WWE (English) ROMs, but there is no reason the shouldn't work on other ROMs, just make sure to uninstall other Japanese enabling software like decuma, CE-star, Askul's letsjapan... I decided to break this functionalities into three different CABs, in case someone only needs to display Japanese text, etc...
1. Displaying Japanese text
This one enables displaying of Japanese characters, like reading Japanese web pages, or using it for various Japanese dictionaries... The CAB is based on Askul's LetsJapan No6, but newer version of wince.nls taken from SoftBank Japanese X05HT 3.39.762.3 WM6.1 ROM. It should work on all devices, despite screen resolution...2. Japanese Advanced IME
LetsJapan WM6.1 r07
LetsJapan WM6.1 r09, Mincho (Serif) font variant. This variant will take about 10MB on your device.
This is a new thing. It enables word prediction input in both English and Japanese, and unlike traditional WM5 & WM6 Japanese IME engines, SoftBank introduced this new IME in its newer ROMs. After installation, KeyTouch IME will become default. It only works in portrait mode, and in the case of landscape mode, IME will change to classic romaji or kana input. Kensaku and Tegaki IMEs are included. Also, settings for Japanese keyboard layout are in this CAB, so if you are using some different layout, you are on your own (there are plenty of posts around which explain how to change this). This CAB is only for VGA (480x640) devices (Planning to make QVGA version too, stay tuned)3. SoftBank MMS
Japanese Advanced IME r07
Finally, people, this was tough nut to crack. The CAB here should work on any english ROM, but i had time to test it only on official HTC WWE. It will also install Softbank Internet connection (opensoftbank, that will NOT be defaulted), because a special connection GUIDs are required, so it is best to install this after hard reset. Also, it's heavily integrated into system, hard-reset to uninstall...4. SoftBank manilla (TouchFLO 3D)
The bad thing is that SB MMS application is in Japanese only, and integration with WWE manila / TouchFLO is poor. For that sake, i managed to adopt SoftBank's manilla, check the 4th CAB in this post.
Good thing is that SMS & Sメール works in both directions. And, tatatattaaa, in combination with my Japanese IME CAB emoticons finally work as desired!
This CAB is based on extracted ArcSoftMMS version 184.108.40.206 files from SoftBank Japanese X05HT 3.39.762.3 WM6.1 ROM.
Please report any issues you may find...
Anybody interested in helping translating some MUIs ???
SoftBank MMS r093
This is just a manila / TouchFLO from SoftBank, in English, to support proper integration with MMS...
(Disable TouchFLO 3D in Today settings before installing)
Disclaimer: the above CABs worked for me but I take no responsibility if you break your phone with them, get outrageous Internet bills, your girlfriend / wife suddenly starts to cheat on you or whatever... Use them at your own risk.
Also, some of the files from this CABs may be found on SoftBank X05HT / X04HT ROMs only, you may legally use these CABs only if you own these phones.