Police on Friday questioned sumo grand champion Harumafuji on a voluntary basis over an allegation he assaulted a lower-ranked wrestler during a drunken brawl.

The government the same day expressed regret over the case engulfing the traditional Japanese sport, which was recently regaining its popularity after its reputation was tainted by scandals over match-fixing, violence and bullying.

According to investigative sources, the 33-year-old yokozuna allegedly hit 27-year-old fellow Mongolian wrestler Takanoiwa in the head at a restaurant-bar around the night of Oct. 25 in the western Japan city of Tottori during a regional tour.

However, details of what happened are still unclear with people concerned offering differing accounts.

The victim, an eighth-ranked maegashira, was injured and has not fought at the Kyushu Grand Sumo Tournament that started Sunday. A medical certificate disclosed by the Japan Sumo Association on Monday showed Takanoiwa sustained injuries on Oct. 26 and that he was hospitalized in Fukuoka from Nov. 5 to 9.

Harumafuji, a nine-time tournament winner, has spoken little in public after the scandal came to light, only apologizing for causing trouble. He has pulled out of the Kyushu tournament.

With investigations continuing, some questions have emerged over how badly Takanoiwa was beaten by the 1.86-meter tall wrestler weighing around 140 kilograms.

The yokozuna was reported to have struck Takanoiwa with a beer bottle in anger as Takanoiwa looked at his smartphone while being scolded for his behavior. But yokozuna Hakuho, who was also at the scene, has said the allegation of the beer bottle strike was inaccurate.

According to the medical certificate, Takanoiwa was diagnosed at a hospital in Fukuoka with a suspected fracture at the base of his skull and a cerebrospinal fluid leak, among other injuries.

But the investigative sources say a different medical certificate was issued immediately after the brawl by another hospital that shows him to have less serious symptoms.

The police are looking into the possibility that Takanoiwa's injuries may have worsened during the regional tour.

The sumo association's panel that is separately looking into the case said the Fukuoka hospital is surprised about the way the media has reported Takanoiwa's injuries as serious.

While a fracture was suspected at the time, Takanoiwa should have recovered by now, the doctor who made the diagnosis was quoted as saying.

According to the investigative sources, no one at the restaurant reported the incident to the police or called an ambulance, while it took a few days for a damage report to be sent to the police by Takanoiwa's stablemaster.

On Friday, Japan's sports minister Yoshimasa Hayashi urged the Japan Sumo Association to swiftly get to the bottom of the allegation and report its findings to him. "It's extremely regrettable that such a case happened," he said at a press conference. "In general, we must resolutely seek to eradicate violence among sports athletes."

In the Mongolian capital of Ulan Bator, Takanoiwa's brother Adiya Luvsan, 45, was angry and said Harumafuji should directly apologize to Takanoiwa.

The elder brother also said to reporters that Takanoiwa told him over the phone on Oct. 28 that the wrestler was hit by a beer bottle and the assault was sudden, even though Takanoiwa had done nothing wrong.

But the brother said he is not wishing for the yokozuna's retirement, given that he has heard Harumafuji regrets what he did.

In 2010, then Mongolian grand champion Asashoryu allegedly seriously injured a man in a drunken rampage and later announced his retirement. In the case, police sent documents to prosecutors on Asashoryu and prosecutors decided against indicting him.


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