I was supposed to be listening to the cicadas and the sound of a flowing creek when a Mitsubishi van rumbled across a small steel bridge just downstream. It was probably depositing campers at a nearby tent village, where kids were running around with their fishing poles and pink bed pillows. This was nature, Japan style. I was in Chichibu-Tama-Kai National Park, a 75-minute train ride northwest of Tokyo, with half a dozen other hikers out for a dose of shinrin-yoku, or forest bathing. The Japanese go crazy for this practice, which is standard preventive medicine here. It essentially involves hanging out in the woods. It’s not about wilderness; it’s about the nature-civilization hybrid the Japanese have cultivated for thousands of years. You stroll a little, maybe write a haiku, crack open a spicebush twig and inhale its woodsy, sassy scent.

“People come out from the city and literally shower in the greenery,” our guide Kunio explained. “This way they are able to become relaxed.” To help us along, Kunio—a volunteer ranger—had us standing still on a hillside, facing the creek, with our arms at our sides. I glanced around. We looked like earthlings transfixed by the light of the beamship. Or extras in a magical-kingdom movie. Kunio could have been one of the seven dwarves. Elfin, with noticeably large ears, he told us to breathe in for a count of seven, hold for five, release. “Concentrate on your belly,” he said.

We needed this. Most of us were urban desk jockeys, including Tokyo businessman Ito Tatsuya, 41, standing next to me. Like many Japanese day hikers, he was carrying an inordinate amount of gear, much of it dangling from his belt: a cell phone, a camera, a water bottle, and a set of keys. The Japanese would make great Boy Scouts, which is probably why they make such fervent office workers, logging longer hours than almost anyone else in the developed world. They’ve even coined a term, karoshi, meaning death by overwork. Since he began lollygagging in the woods and picnicking on octopus, Ito’s shoulders seemed to be unclenching by the minute.

“When I’m out here, I don’t think about things,” he said.

“What’s the Japanese word for stress?” I asked.

“Stress,” he said.

WITH THE LARGEST CONCENTRATION of broad-leafed evergreens in Japan, mountainous Chichibu-Tama-Kai is an ideal place to put into practice the newest principles of wellness science. In a grove of rod-straight Japanese red pine, Kunio pulled a thermos from his massive daypack and served us some mountain-grown, bark-flavored wasabi-root tea. The idea with shinrin-yoku, a term coined by the government in 1982 but inspired by ancient Shinto and Buddhist practices, is to let nature enter your body through all five senses, and this was the taste part. I stretched out across the top of a cool, mossy boulder. A duck quacked. I was feeling pretty mellow, and tests would soon validate this: between the beginning and the end of the two-hour hike, my blood pressure had dropped a couple of points. Ito’s had dropped even more.

We knew this because we were on one of Japan’s 48 official Forest Therapy trails, designated for shinrin-yoku by Japan’s Forestry Agency. In an effort to benefit the Japanese and find nonextractive ways to use forests, which cover 67 percent of the country’s landmass, the government has funded about $4 million in forest-bathing research since 2004. It intends to designate a total of 100 Forest Therapy sites within 10 years. Visitors here are routinely hauled off to a cabin where rangers measure their blood pressure, part of an effort to provide ever more data to support the project.