Last week Mitsui Mutual, the weakest of the seven, joined in an alliance with SumitomoMitsuiBank, Sumitomo Life and MitsuiSumitomo Insurance, a non-life insurer.
It is not clear how effective the move will be, though: SumitomoMitsuiBank has massive bad debts of its own and has yet to commit fresh funds to Mitsui.
The FSA's new requirement, likely to be phased in from 2016, is expected to cover major trust banks, such as SumitomoMitsui Trust Bank and Norinchukin Bank.