I have recently purchased an external Japanese keyboard from FILCO.
In addition to the regular keys, it also has 3 keys specifically designated to switch between Western and Japanese character input.
Apple provides the same keys on its Japanese keyboards and they function as expected.
With a 3rd party keyboard however, these keys don't fire at all.
Even when viewed with tools like KeyRemap4MacBook's event viewer, key-presses are not detected as events.
Is this a common issue?
My written Japanese is weak, so my searches in Japanese didn't turn up any results.
Any direct advice or even links to articles in Japanese (or English ones I might have missed) would be greatly appreciated.
Best Answer
Maybe it's not recognized as a JIS keyboard. See http://m10lmac.blogspot.com/2009/12/fixing-keyboard-type-problems.html:
If nothing else works, you can use KeyRemap4MacBook to map other keys to かな and 英数 keys: