Just one measly week ago, with the axe still to fall, the stalwart samurai was the global financial industry’s luscious little secret.

As Wall Street and the City writhed in agony, Japan’s samurai market — yen-denominated debt issuance by foreigners — was a dependable old bruiser with pleasantly deep pockets.

Capital shortage on the home front and screaming shareholders? No problem: Japanese institutions and households have been so starved of yield for so long that they’ll bite your hand off for a coupon of more than 3 per cent. That was the logic and, for institutions in the US, Europe and Asia, it was a compelling way to buy breathing space in increasingly stifling times.

So since the credit crunch hit home in 2007, everyone has been discretely sidling up to the samurai and tapping him for more cash to fill their fast-depleting war-chests of capital. Citigroup recently issued the biggest samurai bond, targeting retail customers in its bid to raise Y315 billion (£1.7 billion) of yen debt. Great warriors such as Goldman Sachs and Royal Bank of Scotland have also come to the samurai to meet funding needs, and Japan has been ready and waiting with the loot.

The collapse of Lehman and the near-miss with AIG now looks horribly likely to scupper that tidy little arrangement and, with it, one of the more useful pipelines of capital in grim times.

Deutsche Bank yesterday admitted that it would be postponing its planned issuance of samurai bonds and, given the queue of others that had been plotting to hit up the Japanese later this year, Deutsche is unlikely to be the last to have cold feet.

To make matters worse, the Japanese may be about to see something very unsettling indeed: if (as many suspect it will) Lehman defaults on its Y195 billion of outstanding yen-backed bonds, it will be the worst samurai default on record. That will be bad news for the many regional Japanese banks that held Lehman’s debt, and potentially catastrophic for samurai debt appetite.

The coming calamity for samurais is now double edged. Primarily, there is the dread of risk. Despite a brief moment of madness 20 years ago, Japanese institutions and households are a naturally cautious lot. It is only because they are living longer and because their savings have been earning them next to nothing that Japanese families have quite recently been persuaded to put some of their £7 trillion of assets into “riskier” investments.

By most gamblers’ standards, the apparent “risk” of bonds issued by once highly rated Wall Street banks was not exactly roulette, but for many Japanese households it was a bold step into the investment casino.

Deutsche’s postponement of samurai issuance to institutions suggests that it knows the professionals in Japan are feeling nervous. If the households’ newly-emerged mood of bravery is shattered as well, samurai debt issuance will slow to a trickle.

But the samurai issue also points to a looming crisis of branding that could be felt most keenly in Tokyo. Japan has led the rest of Asia into a spiral of brand obsession that has burst out of the boutique and the supermarket into all areas of life. Wall Street, despite a history of meltdowns and failures, used to be up there in the Japanese mind with Louis Vuitton, Chanel and Hermes. The lesson that Japan will take from the past three days is that America’s financial brands are anything but an assurance of quality, whatever the credit ratings agencies are currently saying about their debt.