Um, keyboard is actually completely supported. I play this game with keyboard too. The keyboard is not recognized only if two controllers are already connected OR a device connected to your PC "fakes out" as a keyboard.
The default controls for keyboard are Arrow Keys for movement, C = selection, X = cancel, following the convention of Japanese PC games. They are mentioned in the first pop-up that asks you if you want to play the tutorial





Just a little something to celebrate the game's launch =P