An ancient pond; a frog jumps in; the splash of water. You don’t have to study the expansive haiku of Matsuo Basho to appreciate that things happen slowly in Japan. According to dealReporter data, the typical gap in Japan between confirmation of M&A discussions and confirmation of terms is about 150 days – three times Asia’s average.

Investors were braced for a similarly leisurely timetable from Sumitomo Trust & Banking and Chuo Mitsui Trust, the country’s number five and eight banks by market capitalisation, which confirmed reports of merger talks on Friday. The combined operation would become Japan’s largest trust bank, with $2,000bn of assets under custody, and its largest asset manager. But even by Japan’s standards, this will be a painstaking affair: the two sides are giving themselves 18 months to form a holding company, into which they will merge the businesses by April 2012. Synergies could amount to $600m, assuming the removal of 15 per cent of joint costs, but investors seem unwilling, or unable, to look that far ahead. STB’s shares barely twitched, while smaller, less profitable CMT – almost certain to be the junior partner in any permutation – slipped 2 per cent.