Tokyo — Company president Tomoo Tokosue voluntarily retired recently with a surprisingly candid confession that he could ''no longer cope with rapid business changes.''
Mr. Tokosue's move is indicative of the major upheavals that are occurring in Japanese board rooms. Many corporations are drawing upon the ranks of younger executives to cope with high-tech business redevelopment in an age of slow economic growth.
Typically, in most Japanese companies a man has plodded slowly through the ranks over a lifetime career, keeping out of controversy and trouble, learning a little about everything but being an expert in nothing - a good committeeman.
Now the era of rule by the technocrats has arrived, and the senior executives that compose a ''gerontocracy'' - government by old men - are in many corporations being retired.
Most of the new presidents are assuming office at a much younger age than their predecessors, part of an accelerating trend toward promotion by merit rather than mere age.
The Wako economic research institute says a record 172 companies listed on the Tokyo Stock Exchange changed presidents in the first five months of this year. The previous record was 164 companies in the whole of last year.
Of the new appointments, about three-quarters drew from relatively younger ranks. Only 40 were men born before 1912.
A typical case was the departure of Mr. Tokosue, president of Teijin Ltd., a former textile giant turned into a highly diversified industrial corporation.
Founded in 1916, Teijin developed into Japan's largest synthetic fiber and textile producer. In recent years, as the textile business declined, it began branching out into such fields as as pharmaceuticals, polyester videotapes, and genetic engineering.
But that took the company far beyond the realm of its president's business experience. Announcing his retirement, Tokosue confessed: ''I've read books on the introduction of biotechnology over and over, but haven't understood any of them really well.
''It's because I'm not a technologist, much less a scientist. So I have decided to quit in the belief that only someone with a technological background can now be a leader of a corporation like ours.''
Thus, for the first time in its 67-year history, Teijin has a technology-oriented - rather than business-oriented - president, Sashiro Okamoto.
Also stepping down was Masao Funabashi, president of Furukawa Electric Company, with a long history as a leader in manufacturing industrial electrical equipment.
''I am giving up because I don't understand technology well,'' Mr. Funabashi said in handing over the reins to Etsuji Kusakabe, a technologist vice-president.
As far as general business policy was concerned, Funabashi was confident of his ability to lead the company. But like so many others in recent months he found that this is no longer enough to cope with the bewildering and lightning-fast technological changes occurring.
Take the case of Nippon Kogaku KK, well known worldwide as the maker of the Nikon brand of single-lens reflex cameras. The company president, Takateru Koakimoto, recently stepped down in favor of vice-president Shigetada Fukuoka with the remark that ''I'm too old to cope with the rapidly changing market.''
A conservative advocate of the reliability and good picture quality of standard 35-mm cameras, Nippon Kogaku has found itself steadily upstaged by a change in consumer demand toward smaller, easier-to-operate electronic cameras, especially those that now combine the latest computer chip technology.
Ishikawajima-harima Heavy Industries Company (IHI), an internationally known heavy industrial giant with shipbuilding, machine building, engineering, aircraft, and aircraft engine divisions, also recently announced changes at the top.
Taiji Ubutaka, a big name among Japanese industrialists, made way for Kosaku Inaba, a turbine and aircraft engine specialist.