On a hot, damp, late-summer afternoon in Tokyo’s Sendagaya district, the part of the city preferred by Japanese fashion and garment companies—World, one of the country’s largest apparel firms, is around the corner; Comme des Garçons­ is a few blocks away—36-year-old Nigo, the founder, president, and designer of the streetwear brand A Bathing Ape, talks obsessively about death. His death. Which is ironic, considering that his brainchild is thriving as few streetwear brands ever have, its sneakers and hoodies breathlessly pursued by hipsters from Harlem to Hamburg.

This is a thrilling, precarious, and potentially lucrative time for Nigo. His company will either get megabig—becoming a hip-hop Polo—or it will maintain its subcultural cachet and take a pass on all those millions. It is, in short, a moment rich with opportunity rather than fraught with death.

Yet as he sits at his museum-catalog-ready Jean Prouvé dining table, Nigo, whose real name is Tomoaki Nagao, continues his morbid talk. He doesn’t want children, won’t consider owning a pet, and blames himself for the failure of his marriage to singer and dancer Yuri Ichii, a union that ended five years ago because of what he describes as his unwillingness to care about anyone more than he cares about himself and his work. “I guess I am a child,” he says. “I will always be a child.”

And it's with juvenile petulance that he talks about how Tokyo’s fashion community has turned its back on him, dismissed him, even laughed at him. "When I die and they make an auction catalog of all my possessions," he says, "then they will understand. Then they will see how important I am."

It is a depressing boast, the angst of an adult expressed through the emotional filter of a child, a pouty version of "Whoever dies with the most toys wins." He repeats the assertion then says he wants to show me some of his toys—his three floors of lunch boxes and Star Wars action figures and Pee-Wee Herman play sets and G.I. Joes and Colonel Sanders statues. He then moves on to the grownup toys: the Bentleys and Lamborghinis and Franck Muller watches and Warhol paintings and Ettore Sottsass sculptures and Futura 2000 prints and Rose Cabat ceramics, as well as the roomful of vintage Louis Vuitton steamer trunks. And then there’s the warehouse outside Tokyo, as capacious as an airplane hangar, that’s filled with the Americana that Nigo scours the U.S. Midwest for—more toys, more plastic figures, as well as vintage jeans and antique Coke machines and Mr. Peanut outfits and jukeboxes and toilet seats that play "(We’re Gonna) Rock Around the Clock." The stuff is unloaded from trucks and unpacked, photographed, cataloged, and prepared by a half-dozen employees so that when Nigo next visits, he can sit at his Prouvé desk, play with his toys, and dream that someday, someday, Tokyo’s fashion world will understand.

Earlier that day, on a quiet, narrow road down the street from one of the Tokyo Bathing Ape stores, I met Toby Feltwell, a 33-year-old English nonpracticing solicitor with brown hair, a broad nose, and a beard, who was carrying a handkerchief to mop the sweat off his brow. Feltwell is the head of international development at A Bathing Ape, or Bape, as it is known. During the past five years, the Nigo-designed $300 camouflage hoodies and the $190 patent-leather Bapesta sneakers have become the outerwear and footwear of choice for rappers and style-conscious musicians—and sought-after status symbols for the millions of teens worldwide who watch music videos on YouTube or MTV. For the past two summers, in hip-hop and urban-music videos, Bape imagery—the Bape logo, the gaudy-colored sneakers, the zip-to-the-top ­hoodies—seemed almost as ubiquitous as Cristal champagne and well-endowed females.