The hand-written sign pinned to the door of the Michinoku stable is apologetic but firm. Visitors are not welcome. It used to be one of the most friendly and welcoming sumo stables in the Ryogoku district of Tokyo, within a stone's throw of the Kokugikan stadium, with casual visitors invited to watch the wrestlers going through their exercises and training rituals.
But even this stable, headed by Kazumi Yoshinaga, who wrestled under the name of Kirishima and held the second-highest sumo rank of ozeki in the early 1990s, has closed its doors to keep out the scandal that is engulfing the sport.
'They're trying to put a good face on it, all the stables in the neighbourhood, but it's hard,' says Doreen Simmons, a devotee of the sport since first moving into Ryogoku 32 years ago and now an English-language commentator for broadcaster NHK.
'It's a terrible mess really and the whole thing has distressed me personally because I know so many of them as personal friends,' she said. 'I wouldn't like to predict how this is all going to end.'
There had been scandals within the tightly traditional world of sumo for the past few years, with allegations that individual wrestlers had been illegally gambling on the outcome of baseball matches, bullying of junior wrestlers and the occasional heavyweight of the ring getting a little rowdy in a bar, but the Japan Sumo Association always slapped a few wrists and managed to smooth things over.
But this time, things are very different. This time, long-time watchers of the sport say, wrestlers confessing to throwing bouts, accepting bribes and running up huge gambling debts have shaken the foundations of a sport whose history is lost in the mists of time. It is possible that, as a result of the scandals engulfing sumo today, its future may be very different.
And, perhaps not surprisingly, the sport's problems can largely be traced back to Japan's yakuza gangs.
In July 2009, a parade of around 50 of the highest-ranking members of the Kodo-kai, the most influential underworld group in the city of Nagoya, made an ostentatious entry into the stadium hosting the tournament. In front of television cameras broadcasting the bouts live across the country, they swaggered in and took up the best seats in the house, right beside the raised clay ring known as the dohyo.
'It was planned and it was deliberate,' said Simmons. 'One of their top bosses had recently been sentenced to prison and one of the few television programmes inmates in Japan can watch is sumo, so they were sending him a message.'
The sight of yakuza smiling into the cameras and sending little hand signals was too much for NHK and the police, who had been investigating allegations of illegal activities within the sport for at least a year. And if the sumo association had been hoping that by issuing mild punishments to a couple of stable owners - who claimed they had merely given tickets to the gangsters' seats to acquaintances - and tightening up rules on the allocation of tickets, they were wrong.
The police stepped up their investiga-tions, and leaks began to find their way into the Japanese media.
Jake Adelstein, a former journalist with the Yomiuri newspaper and author of Tokyo Vice: An American Reporter on the Police Beat in Japan, is under no illusions as to where the information came from.
'Tokyo governor Shintaro Ishihara had no interest in investigating this as a legal problem - this is a man who said we should view sumo like kabuki and just sit back and watch it for amusement - so this whole scandal has finally come out because of police leaks.'
And as a prosecutorial tactic, it has been very effective.
To date, the Japan Sumo Association is carrying out an internal probe that has implicated 14 wrestlers and elders of the sport in rigged bouts. Two wrestlers, Chiyohakuho and Enatsukasa, admitted match-fixing, along with a an elder of the sport, Takenawa. Another wrestler has been found guilty based on incriminating text messages.
The association cancelled the tournament in Osaka scheduled for this month and says a basho (tournament) in May in Tokyo will only go ahead if it has completed its investigation satisfactorily. There are suggestions that it is being stonewalled; only seven of the 14 implicated in the scandal have handed over their mobile phones - and of that seven, three were broken.
Adelstein, for one, is not surprised.
Betting on baseball matches by sumo wrestlers has been whispered about for years, he says, but the problem really came up when the underworld got involved in what had been quiet hands of cards played in the stable for a couple of thousand yen.
'Some of these young wrestlers ended up losing a lot of money to yakuza, who also like to bet illegally on the outcome of sumo bouts,' said Adelstein. 'That gave the gangsters the influence over the wrestlers to fix matches. And once the yakuza get into anything that makes them money, they will take it over.'
Japan's national sport has been in the doldrums for a decade or more, partly over bad press and partly, some say, because an influx of foreign wrestlers - primarily from Mongolia, which has its own tradition of wrestling - simply wanted the money handed out to tournament winners more than a generation of young Japanese who have been cosseted rather than told to fight for their dreams.
In June 2007, 17-year-old Takashi Saito was admitted to a hospital in Nagoya with severe bruising that his fellow wrestlers and stable master Junichi Futatsuryu claimed was the result of a training accident. Wrestling as Tokitaizan, the boy died and an autopsy showed his injuries were not consistent with an accident.
Futatsuryu and three wrestlers were arrested nine months later after police learned that Saito had tried to run away from the stable because he found the systematic hazing and physical demands of the training too tough. Caught by his fellow rikishi, he was taken before Futatsuryu and beaten around the head with a beer bottle. The stable master then ordered the other wrestlers to continue the assault, using a metal baseball bat.
In 2002, questions were asked in the Diet about wrestlers taking performance-enhancing drugs designed to give them the perfect combination of power and speed, but equally delaying their recovery from injuries. Kenshiro Matsunami, a member of the New Conservative Party, pointed out that the average weight of a wrestler has increased by 40kg in the past four decades. They now generally weigh in at 155kg.
In January 2007, Asashoryu - a Mongolian who attained the highest rank of yokozuna - was implicated in match-fixing claims that saw the JSA question dozens of wrestlers, all of whom said: 'I have no recollections of that.'
Nothing came of the investigation, which came seven years after the previous suggestion that bouts had been rigged. Many believe it was no coincidence the two wrestlers who made the initial complaint of fixes in 2000 died within days of each other of mysterious liver complaints.
The cumulative result has been that stadiums that were once sold out for tournaments now have empty seats, NHK has chosen not to cover every day of some tournaments live and a publishing affiliate announced on February 20 that it was shutting down its sumo magazine.
The biggest fear is the government will withdraw sumo's protected, non-profit status, which would mean that the guarantees that it could never go bankrupt would go away. And, if it were to find itself in a similar position to so many Japanese companies, bankruptcy could be its fate.
'Sumo has never been in a worse position that it is now, excluding immediately after the war when all the facilities had been destroyed,' said Adelstein.
The difference between then and now is that the sport was on its knees due to influences beyond its control and there was a determination to rebuild what was seen as an integral part of Japanese culture and national identity. The sport today has been laid low by its own actions.
'It's a farce,' said Adelstein. 'I expect the investigating committee will deliberate, postpone its findings and make massive apologies, but there's a Japanese saying that goes: 'Any scandal lasts 75 days and then it is forgotten.' And that's what they're hoping for.
'But for a lot of people, it's right up there with pro-wrestling now.'