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.

Masahiro Nakai, one of Japan's top TV hosts and a former pop star, says he is retiring to take responsibility over sexual assault allegations.

Nakai’s decision came following reports that he engaged in non-consensual sexual activity with a woman that led to a settlement with the victim.