SUMO grand champion Harumafuji has decided to retire after allegations that he assaulted a lower-ranked wrestler and tarnished the image of Japan’s national sport.

“I have caused much trouble to society,” said the Mongolian at a packed press conference yesterday. “I want to apologise to various people in the sumo federation who have supported me. As a grand champion, I have done something that shouldn't be done.”

The news dominated Japanese television talk shows and evening newspapers for weeks as the nation expressed shock at claims against a yokozuna grand champion, whose behaviour in sports and society is expected to be exemplary.