Monday October 27 in Tokyo started out sunny and clear, but by around 4pm ominous black clouds filled the sky and by 5pm there was total dark before the first flashes of lightning began to strike over the citys skyscrapers. As a metaphor for the countrys fortunes over the last few months this would be hard to improve on: after a period in which Japans banks seemed to have risen above their stricken peers, that Monday saw the Nikkei 225 index fall to a 26-year low.
The banks fortunes plummeted almost in sync: their fates are, to a degree perhaps unparalleled elsewhere among sophisticated markets, tied to the domestic stock market. Hajime Kitano,...