The bank, SBI Sumishin Net Bank Ltd will compete against online lenders for a share in the $13 trillion household financial assets market.
The Dutch group, ING Direct expects to bring an online bank to Japan by the end of the year and could provide competition for SBI Sumishin.
The launch of the bank is scheduled for September 24th depending on regulatory approval, and would offer deposit services, money transfers and housing loans via the telephone and online.
The bank wants about 600,000 accounts by its fifth year and $8.8 billion depositis.
The bank will be half owned by SBI and Sumitomo Trust and they will share the investment of $176 million.
The bank will also make online trading easier for its customers by using its ties to SBI E*Trade Securities Co Ltd, another SBI unit.