“They call it corporal punishment,” he said, “but more precisely, it’s violence and abuse.”

The problems go beyond youth judo. A high school basketball player in Osaka killed himself in December after constant abuse from his coach. In January, the coach of Japan’s national women’s judo team resigned after admitting he had physically abused 15 team members in the run-up to the London Olympics.

This prompted the Japanese Olympic Committee, which is bidding for the 2020 Games, to survey thousands of athletes and coaches among its 57 member federations. Last month, the results were announced: More than 200 athletes said they had suffered sexual harassment and physical violence from their coaches. The same day, the committee announced it would cancel ¥25 million, or $260,000, in annual funding to penalize the Judo Federation, saying that such abuse in sports was strictly prohibited.

Murakawa said he held the Judo Federation and the education ministry accountable for maintaining ignorance about judo’s dangers and for allowing a culture of abuse to go unchecked for so long.

“We Japanese are also to blame for this,” he added. “We have accepted violence and allowed it to keep happening.”

Yukio Sato, chairman of a special committee on safety instruction for the All-Japan Judo Federation, defended the group, saying it was not in a position to keep close tabs on school programs. (He did say that its safety guidelines, which did not adequately address concussions until 2011, fell short.) The latest effort, he said, is to improve instructor quality with a licensing system — mandatory only for federation members — that was instituted when the school year began earlier this month.

The education ministry has also taken steps toward increasing judo safety. It began issuing warnings about head injuries after the Japan Judo Accident Victims Association conference in 2010. However, Toshima, of the Sports and Youth Bureau, declined to say when the ministry had become fully aware of the problems. In 2012, when judo became compulsory in many schools, the ministry published revamped safety guidelines. In addition to updating its policy on corporal punishment in schools, it reaffirmed the need for every municipality to report school accidents.

It remains to be seen what effect the changes will have, but they are unlikely to console families like the Kitagawas, whose son Daisuke has been in a vegetative stupor for five years.