The death of a teenage sumo trainee, who was beaten savagely by his stable-master and bullied mercilessly by older wrestlers, has thrown open the secretive world of the national sport of Japan and horrified its fans.

Match-fixing allegations and other scandals that have arisen this year have already dented sumo’s image as a sport of noble traditions and samurai honour.

Yesterday’s tearful public appearance by the father of the dead boy is likely to destroy the dignified image of sumo for ever. The death of 17-year-old Takashi Saito has exposed it as a murky domain where bullying is rife and violence is part of daily life.

Masato Saito begged the sport’s authorities to end their cover-up of his son’s sudden death. Weeping, he demanded that the Sumo Association tell the truth and take steps to prevent a repeat of the abuse that cost the life of Takashi.

In what would be the first arrest of a sumo stable-master, police sources said that they were likely to charge Junichi Yamamoto in the next few days with causing the death of his teenage jonokuchi – the most junior rank of wrestler.

The life of aspiring young sumo wrestlers is notoriously tough, but until yesterday it was always assumed that the stable-masters had the best interests of their wrestlers at heart and knew where to draw the line.

As details of Takashi’s death have trickled out – officially he died from heart failure in June while preparing for a tournament – a grim reality has emerged. Hit repeatedly on the head with a beer bottle by his instructor, kicked by his fellow students and later pummelled with a metal baseball bat, Takashi’s short career in sumo has been exposed as a daily ordeal.

He ran away twice from the stable but was forced back into the fold by older wrestlers. As punishment for his desertion, his mobile phone was smashed to bits to deny him any contact with his family and the outside world. In a move that Mr Saito now regrets bitterly, he told his son to stick it out rather than quit.

On the day before his death Takashi was forced to endure an ordeal that coroners at Niigata University believe may have led to his death.

As part of their training regime, wrestlers are put through regular sessions of butsukari geiko – a bone-crunching process in which young sumo are repeatedly charged into by their peers to prepare them for the violence in a match.

Butsukari geiko is so fierce that wrestlers are limited to only three or four minutes. On the day before he died Takashi was exposed to 30 minutes of battery by bigger, stronger wrestlers.

The aftermath of his death has revealed increasingly desperate attempts by the stable-master to cover up what went on at his school.

Initially, Mr Yamamoto denied that there had been any violence involved in the boy’s death. Then Takashi’s parents became suspicious when the stable-master offered to pay for a quick cremation of their son. When the body was returned to them covered in bruises and scars, they demanded the postmortem examination that revealed what had happened.

The scandal comes as sumo is trying desperately to win back the support of ordinary Japanese – fans who have recoiled in horror at a series of match-fixing allegations and the perceived ill-treatment of its Mongolian grand champion, Asashoryu, who is now receiving medical treatment for a stress-related disorder.

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