Seven years ago, Mr Flowers helped to rescue the fortunes of Shinsei, making massive profits after the bank was relisted.
Since then, he has stayed on at the bank as director with a six per cent stake.
Now Mr Flowers is looking to buy 32.6 per cent in total of Shinsei, as he believes that the investment group can recover after it has already posted a $107 million writedown due to the sub-prime crash in the US.
Mr Flowers is head of a consortium including Banco Santander and Swiss Re, which is offering $1.8 billion for the stake, the Financial Times reports.
The deal, if agreed, would make the group the biggest shareholder in Shinsei and experts think that Mr Flowers must either believe the bank is undervalued or thinks it will find a strategic buyer.