SoftBank Group Corp. is buying alternative-asset manager Fortress Investment Group LLC for $3.3 billion in cash to operate alongside the company's soon-to-be-established technology investment fund.

SoftBank will pay $8.08 a share for New York-based Fortress, a 39 percent premium to the company's Feb. 13 closing price, according to a statement Tuesday. Fortress principals Pete Briger, Wes Edens and Randy Nardone have agreed to continue leading the business, which will remain based in New York and operate independently within SoftBank, according to the statement.

SoftBank's founder Masayoshi Son is in the process of creating a $100 billion Vision Fund with Saudi Arabia and other backers that would make the Japanese billionaire one of the world's biggest technology investors.