Top brass at Japanese network giant Fuji Television and its parent company have stepped down following allegations involving Masahiro Nakai.

The president and chairperson are out after complaints of a lack of transparency surrounding Masahiro Nakai in Japan

The spiralling controversy involves Masahiro Nakai, the 52-year-old media personality who was the leader of defunct male idol group Smap, and mainstream broadcaster Fuji Television. It also highlights the growing role that foreign activist shareholders are playing in compelling change in stuffy Japanese boardrooms.

Japanese TV network Fuji faces mass advertiser exodus after allegations of covering up sexual assault claims against host Masahiro Nakai of SMAP fame.

Masahiro Nakai, one of Japan’s top TV hosts and a former pop star, said Thursday he was retiring to take responsibility over sexual assault allegations that are part of a wave roiling Japan's entertainment industry and have triggered an avalanche of lost advertising at one of the networks where he worked.