The nagging fear is that Japan's lenders - the conduit for the world's greatest stash of savings - have taken on a far bigger chunk of mortgage securities, collateralised loans obligations and other exotica from America's structured credit boom than they have yet revealed.
Americans and Europeans have so far confessed to $130bn of the estimated $400bn to $500bn of wealth that has vanished into the sub-prime hole. Somebody, somewhere, must be sitting on a vast nexus of undisclosed losses. We may find out soon enough whether the hold-outs are in Japan. The banks have to come clean under the country's strict new audit codes by the end of the tax year in March.
"We think this is where the next big problem is going to pop up," said Hans Redeker, currency chief at BNP Paribas.
"We know from Bank of Japan's lending survey that the banks are already tightening hard, so something is brewing. Right now, we are in the lull before the second storm in global markets, and Asia is going to be the source of the nasty surprises," he said.