It seems that the Tokyo metropolitan area is the world's most populous, with 33.8 million people. Kyoto-Osaka is ranked at number 9, with 16.7 million people. Since I am flying into Tokyo and taking the shinkansen to Kyoto, that means I'll be traveling through an area populated by 50 million human beings.
In comparison, the Houston metropolitan area has only 5.2 million people, which is surprisingly less than the Boston metro area (5.7m) where I spent two years. My hometown of Chicago has 9.7m in its greater environs (Chicagoland). This isn't surprising, given that population density in America is far below eastern countries, but I was surprised to see even mighty Mumbai rank only number 6 (18.8m).
I've seen slums with teeming millions of poor. But what do the teeming millions look like when they aren't in slums, but rather high-rise urban grids? I think I'm in for some culture shock, indeed.