Tokyo — Salesman Ichiro Yamada often drops in for a hasty breakfast of coffee and doughnuts at a ''Mister Donut'' franchise near his office. Too busy for a sit-down lunch, he snacks on a ''Big Mac,'' French fries, and milk shake at the nearest McDonald's.
On his way home at night, he sometimes drops into a Kentucky Fried Chicken outlet to pick up a ready-to-eat dinner for the family.
There may be many Americans who think imported products do not play an important role in Japanese life or that the Japanese actually discriminate against foreign products.
But conversations with a cross section of Japanese from various walks of life reveal this is not true. Most do not make any distinction between domestic and foreign goods, and some even prefer the latter.
In every facet of Japanese life, in fact, imports play their part, and it is often the leading role.
Take food, for example. Economist Hirohiko Okumura takes his family out to dinner every Saturday night and almost always they drive to a nearby Denny's restaurant for a cheap, filling meal.
As for sportswear and equipment, when company executive Isao Takemoto plays golf, he is always impeccably dressed with the Slazenger trademark prominently displayed. His clubs are Wilson, his golf balls Dunlop.
For his birthday, Mr. Takemoto likes his presents to be stylish clothes or accessories with prestigious labels.
What part do imports play in the daily life of auto company official Nobuhiko Yasuda?
''Well, I use a Philips electric shaver and I wear Rodenstock (German) spectacles, which are a very popular status symbol here,'' he says without hesitation. ''I'd also like a Swiss watch, but I can't afford it.''
Looking around him, Yasuda is envious of a family three doors away from his home who spent over a thousand dollars on Finnish white wooden furniture, a dining table and four chairs.
The Japanese spend a higher proportion of their income on clothes than any other nation, and they are the most label conscious. Japanese men are often so proud of the label on their ties they turn the tie around so the label is visible.
The postwar Westernization of the Japanese wardrobe was led by French designers like Cardin, St. Laurent, and Ungaro. But with a more relaxed life style, American-labeled casual clothing and sportswear is now highly prized.
But when not buying for prestige of the brand name, many Japanese are no longer aware that they are buying a foreign product. Some of the latter, in fact , have become totally ''Japanized'' in the consumer mind.
The story is often told of the Japanese schoolboy who went to the United States on a holiday and exclaimed in wonderment: ''Why, they have a McDonald's here, too.''
Sitting in Denny's, Hirohiko Okumura confesses: ''I never knew it was American. . . . I'd always thought Denny's was Japanese.''
In fact, it is a highly successful joint venture between the US coffee shop and restaurant operator and a leading Japanese supermarket chain. In 10 years, 163 restaurants have been established, sales and profits have maintained double-digit growth, and the company's stock has become one of the hottest sellers on the Tokyo stock exchange.
Even so, it has a long way to go to catch up with McDonald's, the country's biggest restaurant chain business.
In 1982 sales topped $304 million. They are expected to reach $370 million this year. Another 50 franchises are scheduled to open, placing the distinctive big ''M'' sign in almost 400 choice locations.
Japan's postwar ''baby boom'' generation, in fact, is hooked on hamburgers and french fries, Shakey's pizzas, Coca-Cola, and Baskin-Robbins ice cream.
Late last year, the semiofficial Manufactured Imports Promotion Committee (MIPRO) conducted an extensive survey of Japanese attitudes to imports.
Among those polled, it found almost 81 percent made extensive purchases of imported foodstuffs, followed by clothing (67 percent), household articles (54 percent), sporting equipment (40 percent), and furniture (18 percent).
Researchers found that when Japanese begin to think more about the quality of living - developing a desire for what many call a ''tasteful life'' - their interest in imports rises considerably.
Tableware and furniture were constantly mentioned in this regard. Among younger people, the top import choices were for sportswear, sports equipment, and cars.
A listing of most popular imported products is headed by black tea, followed by perfumes, whiskey, tableware, fruits, chocolates, jam, sports equipment, cosmetics, and passenger cars.
But in an indictment of foreign companies, consumer consultant Hiroko Kofuji says: ''Although Japanese welcome imports, the fact is that their favorable image here was developed not by the export-to-Japan efforts of foreign companies , but by the purchasing operations of world-famous Japanese trading houses and stores.
''Japanese these days notice a great many commodities they wish to buy when they travel overseas . . . so the potential is there for anyone willing to make the effort.''