Japan is a country known for a lot of things, but in recent years, they've become renowned for their love of sweets. Often, companies will release products exclusively in Japan because they know that the Japanese market is usually a bit more accepting of "non-traditional" recipes — so to speak.
One brand that stands above the rest in their pursuit of non-traditional sweets is Kit Kat. They've dominated the weird Japanese candy market for a while now, and for good reason. Their latest flavor though may have gone a bit too far.