Japan's inbound tourism shows no sign of slowing down, and spending by foreign visitors is also on the rise. But what exactly are they splurging on?

One particular shopping draw is surely Nestle's KitKat lineup. The British-born chocolate bar has become a tourist favorite thanks to a variety of only-in-Japan flavors — from mega-hit green tea to sake, strawberry cheesecake and even wasabi.

But Nestle Japan is dead serious about what some regard as wacky KitKat flavors. In fact, they are the company's answer to Japan's aging society and the way to survive its shrinking market, said Takuya Hiramatsu, an assistant manager at Nestle Japan's marketing and communications division.