United Managers Japan Inc., a hedge fund firm with about $100 million in assets, said its Kotoshiro fund will double in size by May, boosted by a first infusion of foreign capital.

The long-short equity fund, which opened in November to profit from falling stock prices in Japan, will grow to about $30 million, CEO Masahiro Koshiba said.

Kotoshiro has returned 3.2 percent since its inception, compared with the benchmark Nikkei average's 6 percent decline since November to its lowest levels since 1982.