Ono won back-to-back gold medals in the men's under-73 kilograms category at Rio 2016 and Tokyo 2020 and also has a mixed team silver from his home Olympics.

The Japanese judoka will start his course as part of the Japanese Olympic Committee's overseas training programme for coaches and said he "would love" the chance to coach the national team.

"Bouts are a matter of life and death for me," Ono was quoted as saying by Japanese news agency Kyodo.

"I can never take one lightly or go into it with a smile.

"Having experienced winning two straight Olympics at the Tokyo Games, there was no other competition that could fire me up like that.

"I'm certain no other experience will surpass it.

"I'm going to Europe and hope to return home after reconfirming my joy of judo there."

The 31-year-old has six World Championships gold medals and one bronze from 2013 to 2019.

He also won gold at the Jakarta-Palembang 2018 Asian Games and finished on top of the International Judo Federation Grand Slam podium five times.  

Former national team coach and Sydney 2000 gold medallist Kōsei Inoue was among those who paid tribute to Ono.

"After nine years of interaction as his national team coach, I'd say he was the ideal judoka equipped with both offensive and defensive abilities," Inoue, who is also the vice chairman of development at the All Japan Judo Federation, said.

"He had a strong philosophy about his own judo and was a judoka who could fight logically.

"The scenes of him winning the Tokyo Olympics and shedding tears are unforgettable."

Ono defeated Georgia's Lasha Shavdatuashvili, deep into golden score, to be crowned champion at his home Olympics.

His dramatic victory against Georgia's Lasha Shavdatuashvili at Tokyo 2020 came deep into golden score.

Ono said that winning back-to-back Olympic titles was "the most prestigious thing in my life."