THE BIGGEST SIGN of Japan's coming adventure makeover is probably Niseko, a once sleepy ski town on the northern island of Hokkaido. Every Japanese tourism official I've asked about outdoor travel points me to Findlay, the leader of what the Japanese media have termed "the Aussie boom." A wiry 41-year-old with sun-creased skin and a quick smile, Findlay came to Hokkaido in 1989 to work as an instructor for Everest skier Yuichiro Miura, who operated a ski school in Sapporo. After six summers of exploring the island's rivers on his own, Findlay quit in 1995 to start Niseko Adventure Center (NAC), Hokkaido's first commercial rafting service.

Ten years later, NAC has grown into a 70-employee operation that takes 30,000 customers per season, nearly all of

"I walk around here and my eyes pop out of my head with all the opportunities," says Australian businessman Simon Robinson.

them Japanese, down the Class III and IV water of the nearby Shiribetsu, Mukawa, and Toyohira rivers. Findlay has been featured in television, magazine, and newspaper profiles around the country. "At first, people were asking me if it was really possible to raft in Japan," says Findlay, sitting in the airy second-story café in his headquarters. Below us about 100 customers are preparing for or returning from trips. "Now the town is turning into Japan's first true international four-season resort. I get invited to speak across the country in towns that want to do what Niseko did."

One reason Niseko has been able to transform so quickly into Japan's most international resort is that Hokkaido is the nation's least Japanese region. A key agricultural area, the 32,200-square-mile island was annexed by Japan in 1869 and thus missed out on the landmark temples that were built all over the country when the Buddhist clergy held sway, from the eighth to the 16th centuries. Niseko is nestled between three 5,000-foot volcanic cones, all of which are part of a 46,971-acre national park, which also includes three separate ski resorts that join at the top and operate off a single $42 ticket. Combine NAC's success, a lack of cultural resistance, Japan's location almost due north from Sydney (there's only a one-hour time difference), and the fact that Hokkaido's epic winter snows come during the Southern Hemisphere's summer, and people were suddenly thinking Whistler Asia.

"I walk around here and my eyes pop out of my head with all the opportunities," says Australian businessman Simon Robinson, speaking over the din of hammers in a construction trailer crowded with blueprints. Japanese ski towns can be pretty spartan—small rooms with shared bathrooms and no après-ski attractions beyond a few noodle shops. But after a ski trip here with his wife, Robinson began building the first Western-style condos in Niseko in 2003 and now has 69 one-, two-, and three-bedroom units, plus 11 houses, with more on the way. At the same time, travel agents in Australia and Canada began pushing Japanese ski vacations. Niseko now hosts about 15,000 English-speaking visitors a year, and Robinson's entire winter is booked by July. Other foreign developers have followed suit. "We're just scratching the surface," says Robinson. "Guys like Ross have created momentum, and we've picked up on it."

One of the greatest pleasures of doing anything in Japan is following it up with a bath. Ibuprofen's got nothing on a cold beer at one of Japan's natural hot springs (volcanically heated onsen) or public baths (sento, which use tap water).

On the first day of my trip, I dropped off my luggage at the Tokyo home of my friend Brad Bennett—a photographer and 13-year resident of Japan who recently descended Mount Fuji on a skateboard—and headed straight to a neighborhood sento to soak away the 18-hour flight from the States. Thirty minutes and a few beers later, I could already feel myself getting over the jet lag.

The next morning, I met up with my friends Doug Boller, an American IT executive, and Taro Yamada, a chauffeur, in the trendy neighborhood of Futakotamagawa for a mountain-bike ride on the trails that had been our weekend tradition. We rode north from the upscale shopping malls and cafés that surround Futakotamagawa station to the wide, grassy banks of the Tama River, which forms the western edge of Tokyo. After about four miles, we entered suburban Kanagawa prefecture, where miles of singletrack and dirt roads crisscross the largely undeveloped hills along the river's eastern shore. We rode for about two hours, then dropped into town to buy onigiri—rice and fish wrapped in seaweed—and tea, typical Japanese convenience-store fare, which we ate back up in the hills after rinsing off at a temple fountain.

Two weeks later, after I've been biking, climbing, and camping across the country—in between beer-soaked nights in Tokyo—I meet up with Doug, his wife, Takami, and several more friends on Sado Island, a former penal colony 22 miles out in the Sea of Japan. We've come for the three-day Earth Celebration, an international folk-music festival hosted by the Japanese drum troupe Kodo.

Like the rest of the country, Sado is dotted with guesthouses and inns, but we choose to camp on the beach, along with several hundred of the 7,000 festival attendees. The performances take place outdoors, rain or shine—we get both—and are reason enough to make the trip from Tokyo. But between shows, we snorkel in the midday heat, explore the island on our mountain bikes, shop for folk art, and soak it all off in the hot springs.

After a three-hour ride through the island's mountainous interior, I sit under a tree at our campsite with a salmon onigiri and a bottle of oolong tea and watch the sun setting over the ocean. Below me on the beach, someone is playing a Japanese flute. Doug sits next to me and asks the same question I'm asking myself: "So—why did you leave this place again?"