When the agreement is complete – subject to regulatory approvals – the private bank, which oversees Y407.9 billion ($4.09 billion) of assets, will become a wholly-owned part of the SMBC, the latter firm said in a statement.

SocGen told this publication that SMBC had issued an "unsolicited bid" for the private bank, whose assets represent only 3 per cent of all the private banking assets at the French firm. The purchase price is not being disclosed. 

"This transaction is an opportunity rather than a strategic move," a spokesperson for SocGen in Paris told this publication. 

Japan has been traditionally a difficult market for non-domestic banks to penetrate, although some firms, such as Credit Suisse, do operate in the Asian economy. Several banks have retreated: Last year, Bank of America Merrill Lynch - which has sold its non-US wealth arm to Julius Baer - disposed of its Japanese private banking joint venture with Mitsubishi UFJ Financial Group. Credit Suisse has bought HSBC's private bank in the country.

More details on its reasons may come when SocGen issues second-quarter financial results on 1 August. In the first quarter, net private banking income across the whole firm rose 19.4 per cent year-on-year to €43 million ($56.9 million). The firm made no reference to its Japanese private bank in the latest results.

The SocGen business in Japan is a trust bank focused on private banking for high net worth Japanese clients, with services such as portfolio management, investment and trust services.

“With this acquisition, SMBC aims to enhance its high net worth individual business including wealth management advisory services for high net worth individuals,” a statement from the Japanese banking group said.

In separate news, as reported elsewhere this week, Société Générale Corporate and Investment Banking has received a Financial Investment Business Licence in South Korea from the country’s regulator. SocGen said the new licence will enable the bank to conduct financial investment dealings in securities, equity underlying exchange-traded derivatives and over-the-counter derivatives as well as financial investment brokerage activities in securities and equity underlying exchange-traded derivatives.   These activities will operate under a new locally-incorporated subsidiary.