Nishimura and Partners has merged with the international division of Asahi Law Offices, creating Japan's largest legal firm to compete with overseas lawyers who are advising on more hostile takeover bids here.

Nishimura, which represents Bull-Dog Sauce Co. in fighting off a takeover bid from a Warren Lichtenstein Steel Partners fund, combined with Asahi Law as foreign firms such as U.K.-based Allen & Overy LLP expand in Japan.

"Our base is definitely being encroached upon as foreign legal firms make their way into Japan," said Tsutomu Miyano, an attorney at Anderson Mori & Tomotsune in Tokyo. Japanese lawyers need to respond, he said.