The walking cane disguised as a plaid umbrella made no sense. If you needed the cane to help you walk and it started raining, would you have to choose between moving and staying dry?

Hiroshi Sato, whose company markets the device, sniffed a little defensively and said that question is asked a lot. And he had an answer. The cane was for an elderly person who might, from time to time, need something to lean on. Carrying around a cane would be an embarrassment. Leaning on an umbrella occasionally was preferable.

The combination umbrella and cane, priced at $60, was one of the new items his company, Teijin Ltd., showed last week at an exhibition in Tokyo of home care and rehabilitation aids that offered a glimpse at one aspect of Japan's future as an increasingly aged society.

Nearly 130,000 people came to look at the latest gadgets and equipment, from a $5 nail clipper with an attached magnifying glass to a $10,000 ceiling rail system that can hoist a person from a wheelchair into a house. Some visitors came from hospital, welfare and home care organizations. Others were manufacturing and sales representatives. But the biggest group was from the general public--elderly people, couples taking care of their parents, students learning how to be home care helpers and quite a few people in wheelchairs.

Among countries with rapidly aging populations, Japan faces particular challenges. One is the speed with which its society is changing, faster than any other. Today, 21 million Japanese, or one in six, are over 65, and in a dozen years that proportion will increase to one in four.

Another is the emphasis on home care over institutional care for the elderly. Nursing homes have not been built in great numbers over the years because tradition dictates that children, in particular the eldest son and his wife, care for elderly parents, usually under the same roof.

But that family support system, while still greater than in the United States, has broken down during the past two decades. In 1980, nearly 70 percent of the population over 65 lived with their children. Today only 50 percent do, according to government figures.

"Japanese used to have respect toward parents and old people, but in the postwar period that attitude has changed," said Hiroshi Shibata, vice president of the Tokyo Metropolitan Institute of Gerontology. "It's because the older generation lost confidence in their values and did not pass them on to the next generation. The Confucian norms collapsed."

Shibata, 62, said of his four children: "I'm hoping half of them will look after me. But it depends on my attitude from now on. I think I have 15 years to work on our relationship."

Despite the trend, the government's major initiative to deal with the aging assumes people will stay at home, because that is the only way the country can afford to deal with so many senior citizens.

A home-care insurance plan will be launched next April to help families take care of aging relatives. For about $30 a month, people over 65 who require care will get home helpers, home bathing services or access to day-care facilities. Local governments will determine the necessary level of care, up to placing people in nursing homes where available. The services will be offered by an increasing number of private businesses.

They and the manufacturers of home-care equipment expect to tap into savings of the elderly, averaging $200,000 per household for those over 65.

The vision of the future displayed at the exhibition portrayed the elderly at home. A telephone had photographs of people or places instead of numbers on oversized buttons. There were kitchen knives with handles well above the blades, a small rope basket with a crank to wring out washcloths; forks and spoons with large, easy-to-grip handles; tables that adjusted vertically for the comfort of a person in a wheelchair; racks that fit over toilets to provide support rails; Safehip underwear with polypropylene pads to help prevent hip injury in a fall; and a scissors-like piece of plastic with finger rests to hold chopsticks in the ready position.

For stylish and active seniors, lightweight, colorful wheelchairs folded down and packed into a suitcase; canes and crutches were flowered; family vans were equipped with ramps; gardening tools such as spades and small hoes had handles perpendicular to the blade and lightweight golf clubs could be swung from a wheelchair.

Tomoyuki Kasahara, 66, has been coming to the annual home-care exhibition for years, taking careful note of new gadgets and products. "Everyone, including me, will eventually need these things," he said, after looking at one of the cars with a seat that pivots and swings out to lower the passenger to the ground.