On Sunday mornings, teenagers crowd the sidewalks of Tokyo’s Shibuya district until they spill over the curbs and into the streets. They start at Hachiko Square, under a video monitor that takes up the entire face of a glass and steel high-rise, and spread out, 30 or 40 wide in the crosswalks. They mill around displays stacked with new sneakers—Nike and New Balance from the United States, Puma and Adidas from Europe via New York. They gather in a small music store that specializes in the American vinyl records played in Tokyo’s popular soul bars—Grandmaster Flash, Curtis Mayfield, Parliament. They spend 370 yen (roughly $3) at Starbucks for a tall iced latte, which tastes just as it does in Washington, D.C., and is just as overpriced. Like any global metropolis, Tokyo serves up a substantial dose of American culture, particularly to its youth. Sometimes, like Starbucks or Nikes, it is authentic. Sometimes, like a “Harbard University” sweatshirt or a potato salad pizza, it is not. But cultural accuracy is not the point. Less important than authentic American origin is the whiff of American cool.

A few blocks from the Starbucks in Hachiko Square you will find Mandarake, a shop that sells used manga and anime (Japanese comic books and animation, respectively). There is no storefront full of dog-eared comics in plastic sleeves, just a maw of an entrance carved cavelike out of fake rock and flight after flight of stairs down to the basement-level shop. There, comic books and videotapes are stacked to the ceiling, alongside the toys and collectibles they inspired. The real esoterica are under ...