Yamaguchi won an Olympic bronze medal in judo in the 1988 Olympics and is also a former world champion. She teaches at the University of Tsukuba.
"What will these Olympics be for, and for whom?" she asked. "The games have already lost meaning and are being held just for the sake of them. I believe we have already missed the opportunity to cancel."
Japan has officially spent US$15.4 billion (NZ$21.5b) to organise the Tokyo Olympics, and government audits say it may be twice that.
In addition, the Switzerland-based IOC derives almost 75 per cent of its income from selling broadcast rights. Its income has been stalled since the one-year postponement of the Tokyo Olympics, and estimates suggest it could lose US$3-4 billion in broadcast income if these games were cancelled.
Fans from abroad have already been banned, and a decision on local fans is expected later this month. Many signs point to Japanese fans also being banned.
The IOC's plan is to get 15,000 Olympic and Paralympic athletes from more than 200 countries and territories into Tokyo, sequester them in a bubble at the Olympic Village, let them compete and then get them out of Japan within two days of their finish.
Tens of thousands of others will also enter: coaches, judges, officials, broadcasters, media, and members of the so-called Olympic Family.
Senior IOC member Richard Pound said last week it would take "armageddon" to stop the games.
Dr Shigeru Omi, a top medical adviser for the Japanese government and a former World Health Organisation regional director, is putting Primer Minister Yoshihide Suga under increasing pressure to explain why the Olympics should take place.
Speaking in a parliamentary session on Thursday, he said "holding the games in the middle of the pandemic is abnormal". On Friday, also in Parliament, he said holding the Olympics if a state of emergency was still in place "should be avoided".
IOC vice-president John Coates said several weeks ago that the Olympics would go ahead if there was a state of emergency.
Tokyo and several other prefectures are under a state of emergency until June 20.
"It is crucial that we must not let the Olympics trigger a flow of people," Omi said on Friday.
Japan has attributed about 13,000 deaths to Covid-19, and less than 3 per cent of the population has been fully vaccinated in a very slow rollout.
Kengo Sakurada, head of the association of corporate executives in Japan, said on Thursday that no fans should be allowed to attend.
"Many people are feeling extremely uneasy about the safety of holding the Olympics," he said." Even if the infections slowed, no fans should be the rule."