University of Tokyo Graduate School Former Professor Accused in Lawsuit of Demanding Sexual Services and Contract Forgery
“An incident in which a former charismatic professor from the University of Tokyo Graduate School, Japan’s top academic institution, allegedly forced a research collaborator to provide entertainment at sex establishments and other forms of hospitality. A trial was held for a former specially appointed professor who was a subordinate of Shinichi Sato and also received such hospitality. While Sato, the central figure in the case, denies bribery by claiming that the ‘entertainment was compensation for lectures,’ what did his close subordinate say? Nonfiction writer Takehide Mizutani, who observed the closely watched trial, delves into its deeper layers.”
A corruption case involving professors at the University of Tokyo Graduate School has come to light, in which they allegedly repeatedly received expensive entertainment from a joint research partner.
The first hearing of former specially appointed associate professor Ayumu Yoshizaki (46), who has been charged with bribery, was held at the Tokyo District Court on April 23.
Yoshizaki admitted to the charges and argued that the background was the culture of the University of Tokyo School of Medicine, claiming he could not refuse instructions from the powerful central figure, former professor Shinichi Sato (62), who is also facing charges in the same case. However, he frequently offered difficult justifications such as saying he gave in, and it was revealed that regarding the sexual entertainment he received, he falsely explained to the university that it was conducted at Sato’s instruction for the purpose of research on sexually transmitted infections.
According to the indictment, from March 2023 to August 2024, Yoshizaki, in collusion with former professor Sato, received bribes totaling approximately 1.96 million yen on 30 occasions from Koichi Hikichi, representative director of the Japan Cosmetics Association (JCA), who has been indicted for bribery. The benefits included entertainment at high-end clubs in Ginza and visits to soapland establishments, in exchange for facilitating the establishment of academic courses.
Testimony and remorse expressed by the subordinate
At 10:30 a.m. on April 23, in Courtroom 706 of the Tokyo District Court, Yoshizaki, dressed in a black suit, sat quietly in the witness chair. After admitting to the charges with “That is correct,” he was asked by his lawyer whether he deeply regretted the incident and replied “Yes,” continuing:
“I sincerely apologize for causing trouble to everyone involved due to my wrongdoing. I have caused the university president to hold a press conference, the director of the University of Tokyo Hospital to resign, and have caused inconvenience to researchers, patients, and the public, as I held the status of a deemed public official.”
He also revealed that he had donated 1 million yen as an act of atonement and expressed his intention to separate himself from public service.
“I have shown an unacceptable example to young doctors who should be my successors. I will no longer be involved in public service. When conducting research from the private sector, I hope to do so in a fair manner that benefits society.”
It is said that the demands for entertainment at sex establishments by defendant Sato and others began after a business trip to Bangkok in March 2024. It is believed that after an after-hours takeaway experience at a top-class club in central Bangkok, their behavior escalated further and became more excessive.The defendants’ responses to questioning from their defense counsel were mostly expressions of remorse. However, during subsequent questioning by the prosecutor and the presiding judge, they appeared flustered and unable to hide their confusion.
Yoshizaki explained the circumstances of receiving the entertainment as follows:
“It is true that I requested the (entertainment). It is not something that can be justified. I have no intention of denying what happened. My supervisor told me things like, ‘Mr. Hikichi is essentially a sponsor,’ ‘Think of it as part of your work,’ and ‘It would be strange to refuse or turn down an invitation,’ so I felt I could not afford to offend Mr. Hikichi.”
The supervisor refers to defendant Sato, who allegedly held absolute authority within the University of Tokyo, and Yoshizaki argued that the hierarchical relationship left him unable to refuse.
The first instance of entertainment took place on February 14, 2023. Yoshizaki selected a high-end French restaurant in Ginza and emailed Mr. Hikichi in advance, writing: “We have reserved a private room at ◯◯◯, so the three of us hope to enjoy a relaxed conversation over delicious food and wine.”
According to Hikichi, when it came time to pay on the day, neither of the defendants accepted the bill. When Hikichi picked it up, they said, “Thank you.”
The total cost was approximately 156,000 yen.
When asked by the presiding judge, “Did you not say, ‘Please let me pay for my share’?” Yoshizaki replied in court:
“I did try to pay. I pretended to go to the restroom and told the staff I would pay, but I was told that it had already been taken care of and that I should not pay. I ended up yielding to that.”
In such a hierarchical relationship under Sato’s authority, one wonders whether such “going against the flow” would even have been permitted.
Taking a woman home on an overseas business trip
At a press conference held after the court session, Hikichi was asked by reporters whether the claims were true. He firmly denied them, stating: “That is not true. I have never heard Mr. Yoshizaki or Mr. Sato say anything like ‘I will pay for it.’”
After the French restaurant dinner, Yoshizaki later asked Hikichi, “Are there any private rooms in bars?” This led to an arrangement where visits to Ginza clubs were added to their meetings.
After about a year of club-going, through coordination by a research partner of JCA, they went on an inspection trip to Bangkok to observe cannabis plantations. During that trip, it is alleged that both Yoshizaki and Sato brought local Thai women back with them after a night out in the city’s entertainment district.
After returning to Japan, Sato reportedly expressed dissatisfaction, saying, “Even though we pay so much at clubs, you can’t even hold hands or kiss.” As a result, the after-dinner venues were changed to high-end soapland establishments in Yoshiwara costing around 80,000 yen for 120 minutes.
When the prosecutor asked, “Was the soapland arrangement your personal decision? Were you really required to follow everything Professor Sato said?” Yoshizaki responded awkwardly:
“Well, there is a so-called ‘culture of the medical school.’ In that culture, the professor’s word carries significant weight. I graduated from Nagasaki University, and at the time Professor Sato was a dermatology professor there. I followed him from there all the way to the University of Tokyo. His words carried an absolute sense of authority. It’s not that I did absolutely everything I was told, but I would like to emphasize that this kind of background existed.”
After the trial of defendant Yoshizaki concluded, Mr. Hikichi held a press conference. He clearly denied that either of the defendants, Sato or Yoshizaki, had ever offered to pay, stating that such a thing did not happen.The prosecutor then raised a sharp point:
“Another professor involved in the joint research reportedly refused the soapland entertainment, didn’t they?”
Sitting in the witness stand, Yoshizaki defendant shifted his chair with his hand and visibly shrank into himself. He was clearly agitated, and then spoke in a strained voice:
“This is difficult to make you understand… but if I had said anything that upset Professor Sato, I would have lost my place at the University of Tokyo dermatology department. I had already severed ties with my medical office in Nagasaki to come to the University of Tokyo, so if I were abandoned here, I would have no idea how I could build my career.”
In this way, Yoshizaki defendant also became deeply involved in the Yoshiwara entertainment, and it was said that he would even talk happily about ejaculating twice, according to Hikichi’s testimony in the same hearing.
Falsifying documents to make it look like he was on the job
The trigger that brought the incident to light was an entertainment gathering in late August 2024, when defendant Sato allegedly shouted at Mr. Hikichi, “Bring 13 million yen, or I’ll kill you!”
Fed up, Hikichi filed a complaint with the police, and the case was later reported by the media, exposing the soapland-related entertainment.
Following the report, the University of Tokyo launched an internal investigation. When Sato was questioned about why he had visited sex establishments, he allegedly presented a business outsourcing contract and claimed it was for research purposes related to sexually transmitted diseases.
When prosecutors questioned Yoshizaki about this document, he admitted to forging the contract and stated:
“It would look bad publicly, so Professor Sato told me it would be better to present it as research. There was discussion about creating that contract, and I acted as the point of contact to handle it.”
In its closing argument, the prosecution described the conduct as planned and habitual, stating that Sato, when absent, reportedly behaved freely and admitted to enjoying the entertainment. It characterized the motive as malicious, driven by pleasure-seeking and sexual gratification, and sought a sentence of one year and two months in prison, along with a fine of approximately 1.96 million yen.
The defense argued for leniency, citing an “absolute hierarchical relationship in which Sato held influence over personnel decisions,” claiming Yoshizaki followed instructions while recognizing the payments as bribes, and that it was difficult to oppose someone he regarded as a mentor. It also noted that he had already suffered social sanctions through media coverage.
When asked by the presiding judge for final remarks, Yoshizaki stood and said, “I have nothing in particular,” before continuing:
“I sincerely apologize for causing trouble. I deeply regret betraying the trust of everyone involved.”
He then bowed slightly.
The verdict is scheduled to be handed down on May 22. What will Sato, who claims that the entertainment was compensation, say in court when he eventually takes the stand?