Hack your iPhone to type in Kanji and Kana
f vi and a bash shell are totally foreign to you, jump to this page
If you are command line (and vi) -friendly:
1. Jailbreak your iPhone, and install the following packages -
1 • BSD Subsystem
2 • Term-vt100
3 • Erica’s Utilities (be sure to edit your path to include /var/root/bin)
2. Fire up the terminal app on your phone and…
cd ~/Library/Preferences
plutil -c xml1 .GlobalPreferences.plist
vi .GlobalPreferences.plist
3. Find the following text:
<array>
<string>en US</string>
</array>
…and edit it to add a line so it looks like this:
<array>
<string>en US</string>
<string>ja</string>
</array>
4. Save and close the Terminal app.
When you visit any application that uses a keyboard now, there will be a globe next to the ‘123’ characters key. Selecting this will alternate between your US and Japanese keyboards. The Japanese keyboard is pretty easy to distinguish, because it is compressed to make room for a kanji/kana suggestion field, and has a long hyphen to the right of the ‘L’ key.
頑張ってください！