One thing you have to give the Japanese credit for: they'll experiment with some crazy flavors of things. Slashfood points out that Kit Kats have exploded over there.
Inventor Spot mentions several flavors, including the one pictured, which is green tea with milk. There's also a "Red Azuki Bean" variation, as well as cherry-flavored white chocolate. Rinkya Blog makes mention of kiwi and orange, to name a couple. Japan Newbie from a while back showed packaging for melon and passion fruit.
They point out the Wikipedia article as well, which lists a crapload of different varieties, including pumpkin and white chocolate with maple syrup.
And here in America we get...chocolate. White chocolate sometimes. Dark chocolate if we're lucky. Bah.