The challenging part of the build was figuring out what the "kana" (i.e.:Japanese) and "Muhenkan" (i.e.:direct type) keystrokes were. I used the HID key reference and the "Key Codes" software to figure out what strokes I needed to issue.
You can see the controller in action on Youtube.
Youtube:Adafruit Bluefruit EZ-Key 12 based foot controller for Mac os