Sumitomo Mitsui Financial Group said Thursday it will acquire a roughly 10% stake in Japanese internet financial giant SBI Holdings in a deal worth ¥79.6 billion ($585 million) to strengthen its online brokerage service.

Through the capital alliance, the two financial giants aim to expand their customer base by making use of SMFG's wide customer base, ranging from retail to corporate clients, and SBI Holdings' younger customers.

In a rare deal for a Japanese banking group to acquire a stake in a major online brokerage, the two companies will expand their partnership from their agreement in 2020 to cooperate in the digital field, which included SMFG's acquisition of a stake in one of SBI Holdings' subsidiaries.