Struggling finance company NIS Group Co. said Monday that U.S. investment fund TPG will become its biggest shareholder by investing about ¥30 billion in the group to help restructure its business.

NIS, hit hard by the tightening of lending rules, will raise ¥20 billion by allocating new shares to TPG on Feb. 20, giving it a stake of about 40 percent, the lender said. The U.S. fund plans to appoint officials to the NIS board to obtain a majority there.

TPG is also set to invest about $102.5 million, or ¥11.3 billion, in NIS' leasing unit in China.