WAS Monday's highly publicized run on a medium-sized Tokyo credit union a conspiracy?
That's what one American investment banker in Tokyo says, though he admits his theory is somewhat far-fetched.
The banker reasons that the neatly timed, orderly collapse and bailout of Cosmo Credit Corporation made the Japanese financial authorities look too good to be true. Patient depositors sat quietly waiting for their money, while clerks poured tea, and trucks stuffed with cash from the central bank and National Federation of Credit Cooperatives sped to the bank's 23 branches in the city.
On Monday, after reports that the credit union faced financial trouble, worried Cosmo depositors liquidated 62.7 billion yen (about $696 million) in funds. By the end of the week, withdrawals had fallen to a little more than $10 million.
Behind the question of the Cosmo bailout lies the larger issue of how and when Japan will deal with its massive bad-loan problem. The Japanese say their banks are carrying some 50 trillion yen, or $555 billion, in bad loans at yesterday's exchange rate of 90 yen to the dollar.
Many observers say they think the estimate is wildly conservative. Japan's central bank and Ministry of Finance are clearly trying to prepare the Japanese public for the expensive task of dealing with the problem. The events of the past week may have given them some needed leeway.
''Just suppose if you wanted public support for a bailout. What would you do?'' asks the banker. ''What about a good old-fashioned bank run?''
Cosmo's bailout was ''beautiful,'' says Alicia Ogawa, an economist at Salomon Brothers Asia Securities. ''After the first day, people began to relax.''
By the week's end, the wreckage of Cosmo Credit Corporation had been neatly cleared away, and Japanese financial officials were well into an aggressive public relations campaign to convince the world that Japan will soon resolve a debt problem nearly 20 times the size of the Mexican banking collapse that paralyzed the international banking community a decade ago.
But the questions are still: How, when, and how much? The Ministry of Finance is developing a five-year plan to resolve the crisis, which it plans to unveil in October, but its content remains fluid. A preliminary set of recommendations submitted on July 25 by a panel of academics is largely seen as a trial balloon.
The main test is whether the Japanese public will tolerate using public funds to prop up the banks. It has never been a secret that what got the banks into trouble was the heady property and stock-market spending spree of the late 1980s, in which many of the bank's best customers were corrupt politicians, stock speculators, and gangsters.
Some within the Finance Ministry oppose the use of public funds, too, but for difference reasons. Japan's public-sector deficit, at about 4 percent of Japan's gross domestic product, is twice that of the US and dangerously high by any standards. Any large-scale bailout of the banks will almost certainly involve deficit financing on a stupendous scale.
So the Finance Ministry's academic advisers concentrated on a relatively modest plan to spend ''several hundred-billion'' yen to help out one of the weakest sectors of the banking system, small agricultural banks that hold about 5.47 trillion yen in uncollectible loans to mortgage companies. Commercial banks exposed to the shaky mortgage companies would pick up their own losses.
Meeting with foreign reporters yesterday, Yoshimasa Nishimura, director-general of the Ministry of Finance's banking bureau, radiated confidence in the government's prospective solutions.
''Invite me to talk to you in five years,'' Mr. Nishimura says. ''I will make the booking and set the theme now: The revival of Japanese banks.''
''Even with the problems we have, we believe it is possible to solve them within the framework of the financial system without resorting to fiscal measures,'' Nishimura says. The uncollectible part of the bad-debt problem is ''only'' 10 trillion to 15 trillion yen, or $111 billion to $166 billion, he said. But Nishimura admitted, too, that all the government's figures are based on the current level of the property market. ''If the assumptions change, the figures will change.''
The admission points to one of the government's worst difficulties - that just as land prices created the problem, they may unravel the solution.
In the late 1980s, a 400 percent rise in land prices fueled an huge spending and lending spiral. Cosmo Credit, for example, although one of the big players, saw its lending nearly quadruple between 1989 and '91. When the land-bubble burst, the banks called in property assets that had been signed over as collateral on loans, only to find the land had dropped so far in value that it would be disastrous to sell.