ENOSHIMA, Japan -- As dusk draped this seaside town in darkness, Ikiko and Kuniyo Hirutani prepared themselves for the unknown. Tonight, they would sleep with the fishes, and both had come prepared -- with sleeping bags and pillows.

The sisters were there with 30 other stressed-out women, ages 28 to 57, seeking inner peace through communion with marine life. For about $120 each, they joined in Enoshima Aquarium's overnight relaxation program -- including a 45-minute session in which the women massaged their arms and legs in a room lit mostly by ghostly, biofluorescent jellyfish swaying gracefully to New Age music.

Before midnight, the sisters tucked themselves inside sleeping bags splayed in front of a vast aquarium wall. They gazed for hours as soothing sea creatures of every size and color glided through the cool blue. "I feel totally relaxed," Ikiko, a 30-year-old apparel company manager from Tokyo, said before she nodded off. "It's like I'm floating, like I'm in the tank with them. Reality feels so far away."

The popular night retreats in this resort town just west of Tokyo are part of a modern search for Zen serenity fueling a $30 billion-a-year business here that analysts call "the healing industry."

It's a little bit California and a whole lot Japan. Although this country has long had traditional shiatsu massage parlors and herbal remedy stores, it's now adding "hot yoga" sessions in 98-degree rooms, aromatherapy, rent-a-pets and "healing houses" equipped with steam baths and light dimmers.

They add up to a pricey panacea in a society where changes in men's and women's roles and in the workplace are piling on stress -- and people have a lot of money to spend in search of relief.

Healing products and services are one of Japan's fastest-growing industries, analysts say, and are helping keep a three-year-old economic recovery on track. A recent study by Mitsubishi UFJ Research and Consulting found that the healing business had nearly doubled over the past decade.

Last year, people here spent six times more on healing than they did on flat-screen televisions and about one-fifth as much as they did on automobiles.

"The Japanese have always had the concept of healing, but the difference is that now we are packaging it and selling it as never before," said Hiroya Kubota, head of a Tokyo-based stress management institute. "Why are we spending so much money on healing? Maybe the Japanese have become too wealthy, our lives too easy. We have no hunger. We have very low poverty and unemployment. Maybe all that wealth has made us see our small problems as overly big and complicated."

But many sociologists say they feel it addresses real needs and problems brought on by a 13-year economic downturn. Though Japan is once again prospering, many people are bewildered by the new roles they are being asked to assume. Company downsizing is undermining the old concepts of lifetime employment and corporate loyalty, promotions and raises are increasingly based on merit rather than seniority, and a new crop of innovative start-up companies is flourishing.

Insecurity about the future is growing in a country that long boasted of being "one middle class" but now appears increasingly divided between a new super-rich class and a relatively poor underclass. At the same time more young Japanese are finding an outlet in kireru -- a sudden burst of violence resulting in injury or murder.

No one has felt the changes more than Japanese women, who have entered the workforce in record numbers in the past decade. As they gain financial independence, women often choose to remain single and childless into their thirties and forties, eschewing the traditional path of marriage and homemaking.

"My mother's generation never had to deal with the work pressures that I face," said Eiko Watanabe, a single, 36-year old data processor who took part in the aquarium's healing night. She spends about $150 a month for aromatherapy and other healing services. Some people spend $500 a month or more.

"I get home at 10 p.m., and I never have a chance to meet men," she said. "When I do, they all have this outdated idea of what a woman should be, and women have gone far beyond that now. It makes me feel very stressed about my future."

"I feel," she said, pointing to a dim tank of soothing fish, "as if I need this."

Spirituality plays little role in individual lives in modern Japan, a historically Buddhist and Shinto society. But that is beginning to change.

Experts cite a proliferation of new religious cults. For the more conventionally minded, there is the rising popularity of the classic Buddhist walking pilgrimage to 88 temples on Shikoku island. At Ryugenji Temple in Kyoto, women can become "nuns for a day" for about $80.

Most Japanese, however, take a secular approach to relieving stress. Luxury day spas and high-end massage clinics have grown 11-fold over the past four years into a $1 billion business, according to Yumiko Arimoto, an analyst at Mitsubishi UFJ. The spas offer treatments such as aromatherapy and Hawaiian Lomi Lomi massages, some costing $300 or more per hour. "Healing has become huge," Arimoto said.

Animal therapy is also expanding, particularly rent-a-pet services that allow clients to enjoy canine or feline companionship without the hassle of ownership. In Tokyo, the number of rent-a-pet stores that hire animals out at hourly, daily or weekly rates jumped more than sevenfold in three years to 115 registered outlets in 2004, the most recent year for which statistics are available.

Once more common on dining room tables here, jellyfish have become the Japanese pets du jour. Enoshima Aquarium marine biologists say their studies prove that observing the slow movements of jellyfish produces a compound in human saliva associated with relaxation. That fact, publicized by the aquarium, is apparently one reason why sales of home jellyfish kits, ranging in price from $200 to over $4,000, are surging.

Meanwhile, the aquarium's own jellyfish are the highlight of its overnight healing tours. The events in which they are featured are so popular that a lottery is used to select participants.

At around 9 p.m. on a recent evening, 30 lucky winners arranged themselves on lounge chairs in the dark room looking on to the home of seven types of jellyfish, including some that looked like frisky, multicolored mushrooms and some slower-moving creatures with elegant, iridescent trains.

As calming music filled the lavender- and tea tree-scented room, experts in Hawaiian Lomi Lomi taught the women how to relax by massaging their arms and legs.

That is how Ikiko Hirutani and her sister, Kuniyo, 28, got back their Zen. "This is exactly what I needed," Ikiko said.

Special correspondent Akiko Yamamoto contributed to this report.