One of sumo wrestling's grand champions has pulled out of the current competition after breaking another wrestler's skull with a beer bottle.
Sumo grand champion Harumafuji has assaulted a junior wrestler, it was learned Tuesday.
Harumafuji, 33, hit compatriot Takanoiwa over the head at a party for Mongolian sumo wrestlers last month, violating the strict sumo rules that prohibit wrestlers from demonstrating their emotions in public, according to Japan's public broadcaster NHK.
Sumo association officials told AFP news agency that exactly what happened remains unconfirmed. He struck Takanoiwa as he did not like his attitude, the report said. The 27-year-old is part of a so-called "stable" led by Takanohana, a former grand champion who reported the incident to police, according to Kyodo news agency.
Another Mongolian grand champion Hakuho, seen as a gentle giant, has nearly single-handedly restored the sport's good name.
Harumafuji is viewed as having a skillful technique that allows him to offset a relatively small body weight - at a mere 137 kilogrammes, he is one of the lightest in the sport's top division.
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The association has questioned the two wrestlers' masters about the incident.
That case exposed a culture of bullying and hazing within the ancient sport's strict hierarchy.
In 2016, a stable master and wrestler were made to pay almost $300,000 (£230,000) to a wrestler allegedly abused so badly that he lost sight in one eye, according to reports.
In 2010, then-yokozuna Asashoryu, also from Mongolia, retired from the sport after allegations he had attacked a man outside a Tokyo nightclub during a tournament.
Violent treatment of apprentices and junior wrestlers in the name of training had always been seen as par for the course at sumo stables, but the sport is now struggling to oust such customs.