Four-time world champion Daiya Seto has been suspended for the rest of the year by Japan's Swimming Federation after having an extra-marital affair.
The 26-year-old has been banned for breaching the governing body's sportsmanlike conduct standard.
The reigning 200 metres and 400 metres individual medley world champion will however be eligible to compete at the delayed Tokyo Olympics next year.
Seto, a bronze medal winner at the Rio Olympic Games in 2016, had already resigned as captain of his country's Olympic swim team last month over the controversy.
He was quoted in Japanese sports daily Hochi Sports saying he deeply regrets his behaviour.
Swimmer Seto to sit out rest of year as punishment for affair: Japanese swimming star Daiya Seto will not take part in any official activities for the rest of the year as punishment for an extramarital affair, the Japan Swimming… https://t.co/NQrCUAXpLl
— Japan Today News (@JapanToday) October 13, 2020
"How can I apologise? I have been asking myself if I can, but I think my apology is to continue swimming, restoring the trust of my family, who have been deeply hurt by my irresponsible behaviour.
"I would like to seriously face swimming with the determination to start over so that my family and everyone will recognise me as a swimmer again. I’m really sorry."
Tsuyoshi Fukui, the managing director of the Japanese Olympic Committee (JOC) and a retired Davis Cup tennis star, says he wants Seto to slowly "restore trust".
Seto has already seen his ties with sponsor All Nippon Airways cut over the affair after a request from the airline.
The Japan Times reports the decision to suspend Seto came about after an extraordinary online meeting of the Japan Swimming Federation yesterday.
Seto had addressed the federation’s ethics committee the day before they came to their verdict.
Tokyo 2021 Games
Japan's Olympic minister Seiko Hashimoto said last month that next year's re-arranged Tokyo Olympic Games must go ahead "with or without Covid."
Hashimoto was adamant they would go ahead regardless of the global pandemic.
"All the people involved with the games are working together to prepare, and the athletes are also making considerable efforts toward next year under the circumstances they've been handed.
"I think we have to hold the games at any cost. I want to concentrate all our efforts on measures against the coronavirus."