Singapore-based hedge fund 3D Investment Partners got two of its nominees on the board of software developer Fuji Soft on Sunday, in the latest proxy fight by activist investors seeking more independent oversight of Japanese firms.

Three battles in recent months have raised questions about how independent from management Japan's outside board members really are after nearly a decade of governance reform has sharply increased the number of independent directors.

Governance experts say outside directors are only nominally independent if they have close ties to management or fail to give proper oversight.