At the age of 42 Hiroshi Yasuda had reached the middle-management level of a major electronics company with a comfortable $40,000 annual salary. But, frustrated by his slow progress up the corporate ladder, he suddenly quit to become managing director of a much smaller company with an immediate $11 ,000-a-year raise. And in doing so, Mr. Yasuda created another small crack in Japan's lifetime-employment system.
Japanese in growing numbers are losing their inhibitions about mid-career moves, opening up a lucrative market for executive ''headhunters.''
Traditionally, major corporations have recruited male university graduates for training as generalists rather than specialists, offering them steady if unspectacular promotion until retirement.
Job changing was discouraged by the fact that a worker joining a new company invariably had to start at the bottom again. The system nurtured a loyal, stable work force, but offered little stimulus to excel or develop full personal potential.
This went relatively unquestioned until the economic shocks generated by the 1973 oil crisis forced enterprises to seek cuts in personnel costs by offering incentives for early retirement, reducing new hiring, and even laying off workers.
With lifetime employment suddenly no longer a cast-iron guarantee, and with the gradual disappearance of the social stigma once associated with job switching, worker restlessness has increased. The prime minister's office estimated that in 1982 a record 900,000 workers were actively job hunting.
The trend has been encouraged by a severe shortage of top-class managers and professionals for the fast growing high-tech industrial sector.
''There is a big demand for engineers and scientists for companies in such areas as semiconductors, computers, biotechnology, and new materials,'' says Seiro Takehara, president of a leading corporate headhunter firm.
''These companies realize the only way to stay ahead in the battle for technical supremacy is to hire the best talent away from other companies.'' Sony , the giant electronics company, adopts this approach, with about half of its managerial staff recruited from other companies.
A spokesman explained that with its rapid growth Sony could not afford to follow the traditional way and wait for younger employees to gain the necessary experience. Instead, it began trimming its university graduate recruit-ment and filling the gaps from the ranks of other companies.
Such ''poaching,'' however, is still frowned upon in most Japanese business circles, and many companies try to avoid trouble by working anonymously through one of about a dozen executive recruitment firms now flourishing here.
Masaru Eshima, head of Tokyo Executive Search, said: ''Ten years ago you invariably got rejected if you approached a potential recruit with a lucrative job offer. But nowadays there are a lot of willing listeners.''
The growing internationalization of the Japanese economy has helped encourage this. Thousands of capable young men are being sent overseas each year. They return full of confidence in their abilities, possibly ''infected'' by the independent ideas they have picked up in the foreign post, and unwilling to accept a system stressing group thought over individualism and promotion by seniority, not merit.
For them, newspapers are carrying increasing job advertisements for top executives with highly attractive salaries in the $50,000-to-$100,000 range.
Some business experts see this as a major trend in the Japanese business world from now on. ''The stress now is on worker specialization. If you don't possess a skill of vital importance you are going to lose out as job openings shrink with industrial rationalization,'' a top Sony official says.
An executive who quit a major Japanese trading firm to work for a foreign company in Tokyo adds: ''The lifetime employment system is a hangover from Japan's era of high economic growth. Now the economy has slowed down, companies no longer have the leeway to set up subsidiaries and offer employees higher salaries and job movements to keep them happy.''
Others play down the trend. Hiroshi Kitamura, an official of Japan's Federation of Employers' Associations (Nikkeiren), believes that lifetime employment is still strong and that the Japanese tendency to stay in the group will probably discourage any major job shifting.
''Workers in smaller companies have always moved from job to job,'' a Labor Ministry spokesman commented. ''It only seems more dramatic now because of the stiff competition between high-tech firms seeking key personnel. . . . But this will pass.''
Perhaps the main beneficiaries of the change have been foreign companies, whose biggest complaint in setting up operations in Japan has always been the difficulty of obtaining top-quality personnel.
According to Mr. Eshima of Tokyo Executive Search, the sort of men seeking to switch jobs today are those desiring more rapid promotion, greater challenge and managerial responsibility, as well as higher salaries. Foreign companies can supply these needs.
Korn/Ferry International-Japan, the local subsidiary of the American headhunting firm, specializes in scouting such talent for foreign companies.
Representative director Akira Arai says company business rose 32 percent from April to October. In fiscal 1982, the firm recruited 58 Japanese executives and professionals for foreign companies here and earned about $640,000 in consulting fees.