Tokyo, Japan, 1948. A man walks into a bank, announces himself to the manager as an official of the local Government Health Department, instructs the staff to take an inoculation medicine and walks out leaving 12 of them dead from poison. Upon first hearing an overview, this might sound like a somewhat unique, but trivial bank robbery. But this is post-war Japan, a country with many secrets and a population with many grievances.

Gold, H. (2011) “Japans infamous Unit 731: Firsthand Accounts of Japans Wartime Human Experimentation Program”. Tuttle Publishing, HK

Trestrail, J H. (2000). Criminal Poisoning: Investigational Guide for Law Enforcement, Toxicologists, Forensic Scientists, and Attorneys. Humana Press, Totowa, NJ. (2019). The Teikoku Ginko Case. [online] Available at: [Accessed 9 Oct. 2019]. (Japanese) (2019). Sadamichi Hirasawa Home Page [online] Available at: [Accessed 9 Oct. 2019]. (Japanese) (2018) Teigin Incident: 70 Years on , efforts continue to clear late artist’s name in 1948 Tokyo mass murder. [online] Available at [Accessed 9 Oct. 2019]

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Sadamichi Hirasawa & The Teigin Incident


Tokyo, Japan, 1948. A man walks into a bank, announces himself to the manager as an official of the local Government Health Department, instructs the staff to take an inoculation medicine and walks out leaving 12 of them dead from poison. Upon first hearing an overview, this might sound like a somewhat unique, but trivial bank robbery. But this is post-war Japan, a country with many secrets and a population with many grievances. This is Dark Histories, where the facts are worse than fiction.

Japan, 1948

During the war, Tokyo, like many major Japanese cities had been heavily carpet bombed. In the final year of the war, 157,000 tons of cluster bombs, many with payloads of Napalm had been dropped over the country, though in history, these raids have been eclipsed by the Atomic bombings of Hiroshima and Nagasaki that nailed home the Japanese surrender. With many of the structures at the time being made from wood, the firebombing devastated cities, leaving 15 million citizens, some 20% of the population, homeless overnight. Fields of stone chimneys struck out of the debris, into the ash filled sky. The Japanese surrender was announced on live radio by Emperor Hirohito on August 15th, 1945. It was the first time for most of the population to have heard the voice of the Emperor, a man they had, up until this broadcast, believed to be the diety of their home nation, a nation whose Empire had a divine, inevitable right to victory.

Less than 90 years prior, Japan had been entirely closed off to the vast majority of the outside world, yet now it suddenly found itself with new foreign masters, as the country became officially occupied by the US under Supreme Commander of the Allied Powers, General Douglas MacArthur. The country was de-militarized and the Empire dissolved. Amongst regret, bereavement, anger at both the Allied forces and the Japanese Emprical throne, a state of emptiness and loss hung heavy over the nation, leaving people with no choice but to find a new way to move forward.

Initially, food in Japan was scarce and sickness commonplace as the rapid end to the war severed Japanese supply lines and saw the return of over 5 million of its empirical soldiers. Black market economies sprung up, alongside alcohol and drug problems. However, democratization of both politics and many of the social aspects of Japan saw the country eventually begin to rebuild, with a new, liberalised enthusiasm. It was a tumultuous, chaotic period, rife with large scale failures and successes, crime and opportunism. In the middle of all of this, a man strode into a Bank in Tokyo, declaring himself to be from the Ministry of Health. He had, he said, come direct from the American central command of GHQ and he had brought medicine.

The Teigin Bank Incident

In the early afternoon, about 3:00am, of January 26th, 1948, the small, wooden pawn shop, recently converted into the Shiinamachi branch of the Teikoku bank, was conducting business in it’s usual way. That is, it was struggling with the usual lack of staff and high turnover of custom. That morning, 7 of the 21 members of staff, including the branches manager had called in sick. Ordinarily, this might have seemed strange, but in post-war Japan, the high levels of fatigue and sickness, due to poor sanitation, homelessness and lack of food had seen many businesses routinely having to cope with a workforce with very little stability. As the remaining 14 members of staff fought through their grinding daily routine, a customer walked in wearing a long brown coat, red rubber boots and a government official armband on this left arm. Upon closer inspection, the armband signified him as a member of the local Ministry of Health and it wasn’t long after he had asked to speak to the branch manager and met with the deputy, that he declared himself as such. He handed over a business card that stated he was a Welfare Epidemologist and though no one who saw the card could later remember the name, they said he seemed calm, respectable and had a medical air about the way he carried himself. He quickly explained his presence at the bank and the present, local situation. A drinking well in the vicinity had been suspected as the cause for an outbreak of dysentry and in attempts to control the outbreak, the  doctor was at the bank to administer medicine in order to  inoculate the staff. The branch deputy was initially wary, however, the doctor reassured him that the medicine had come from GHQ, General MacArthurs offices themself and was good for the cause. By 1948, the Japanese had become accustomed to falling in-line to American orders and in the bank, as elsewhere, the branch deputy conceded and cast away any doubts that he may have had.

There was one small issue, however, the medicine that the doctor bought to help the staff had to be ingested and it had a tendency to damage the enamel of ones teeth, and as such, he would have to demonstrate how to drink it quickly before they were to take it. The branch deputy dutifully collected up the staff members, 14 in total along with 2 members of one of the workers family, and all stood around and watched as, using a small glass, military issue pipette, the doctor dropped some of the medicine into a cup of Japanese tea, poked out his tongue, curling it inwards and downed the drink in one. This was vital, he said, to insure that the medicine does not damage the teeth. He then explained that one minute later, which he would time with his stopwatch, they weer to drink a second medicine and once again demonstrated himself drinking from the small, Japanese cup. He then turned his attention the the 16 cups before him, each filled with a small serving of Japanese tea and once gain suing the pipette dropped a small measure measure of the first medicine into each cup, which the staff collected and all at once, on the doctors word, knocked back the cocktail. A minute passed, the hands ticking on the doctors stopwatch. Some of the staff members complained that it burnt there throats, but they were quickly reassured that the second medicine would calm any irritation. A minute later, they once again, on the doctors word, knocked back the second medicine. Almost instantly, the foul taste and irritation reached a point for the staff that they asked if they could excuse themselves to the bathroom to rinse their mouths and the doctor consented. The deputy too, excused himself. In the bustle of the staff to ge to the bathroom, the doctor casually rounded up his business card and tea cup and collected 164,450 yen from a nearby desk, along with a cheque for 17,450 yen. As the staff began filtering back from the bathroom, many suddenly began to drop to the floor, ill and within half an hour, the doctor stepped over 10 dead bodies, one of which was the 8 year daughter of one of the employees, as he exited the bank. At around 4pm, a member of staff burst from the back door of the bank, screaming for help and the hospital was alerted. 6 members of the banks staff were taken to the nearby Shino-Ochiai hospital, but by the time they arrived, two more had passed away. By the time police had been notified of the afternoons occurrence, the mysterious doctor was long gone.


The police investigation was quick to react. By the next day, an operations HQ was set up with Criminal Director of the Metropolitan Police, Jiro Fujita heading up the investigation. Speaking with. He four surviving witnesses from the bank, one of the earliest steps in the investigation was the construction of the first ever composite photograph used in Japan. Cutting up photographs, police pasted together a montage of the suspect using the eyes, nose and mouth of previous criminals mugshots based on witness descriptions. It was far from perfect and over the span of the investigation, went through ten further amendments. 

The investigation instantly threw up strange questions. Although the culprit had stolen a significant sum of money from the cashiers desk, the equivalent to over 35 years worth of salary from an average university graduate job at the time, he had left behind far more. There was over 410,000 yen left behind in the bank, including 350,000 yen in a single package stored in the unlocked, and wide open, bank vault. Then there was the question of how the supposed doctor had taken the poison in front of everyone when he ran his demonstration, but presumably remained unaffected by the poison himself.

At 2:30pm the same afternoon, a man walked into the Itabashi branch of the Yasuda Bank, 3km North from the scene of the poisoning from the day before and cashed the stolen cheque. Police attempted to follow it up as a solid lead, however soon found that the address given to the bank was fraudulent, with no name or address written on the back for the cheque at all. Having very little else to go on, police took a sample of the mans handwriting and instead focused on trying to uncover any previous potential incidents in the local area. It didn’t take long for this line of inquiry to bear fruit and police soon came across witnesses that were attesting to two potential incidents that had happened in the months and weeks prior. The first took place on October 14th, 1947, three months earlier, at the Sugawara branch of Yasuda bank, 10km to the west of the Teikoku Bank. A doctor had approached the manager and explained a similar story, that the locals were suffering from dysentry and that he was there to administer an inoculating medication from the Ministry of Health. The staff were dutifully rounded up and the medication drank by all, but after waiting around for ten minutes and no effects appearing amongst the staff, the doctor made his excuses, stating his concern for the late arrival of the disinfectant crew, and left the bank saying he would chase them up and return, however, no one in the bank saw the doctor again. At the time, he had handed over a business card with the name of Doctor Matsui Rin. Frustratingly, the branches deputy manager had held his own suspicions over the dysentry story and had snuck out to a phone box to make a call and to check the doctors story with the local authorities. Between them, they quickly uncovered that there was no outbreak of dysentry in the area at all and had rushed straight to the bank, but had just missed the mysterious doctor.

The second similar occurrence had taken place just one week prior to the Teikoku bank robbery, at the Nakai branch of the bank of Tokyo, just 2km away from Teikoku Bank. Once again, it was 3pm when a man strode in, declaring himself to be from the ministry of health and handing over a  business card, this time with the name of Doctor Jiro Yamaguchi. He told the manager that a local family had been suffering dysentry, with the family name Otani and that they had been informed that Mr Otani had visited the bank on that day, therefore all rooms, money and cheques must be disinfected and the staff inoculated. The manager checked to see whether or not the story matched the facts and to see if a Mr Otani had indeed visited the bank. As it turned out, he had and had deposited a large cheque, problem was, his address did not match with he address given by the so-called doctor. When the manager returned and asked him if he had made a mistake, the doctor said that perhaps he had, he would return to his office and check. As a precaution, he took a small bottle of liquid, sprinkled it on the cheque and made a hasty retreat from the bank.

Neither of the two stories had been reported to police and as such, had seen no press coverage, so a copycat robbery was ruled out and the names on the business cards were chased up. Unfortunately, Doctor Jiro Yamaguchi was found to not exist at all and police concluded that the card was more than likely a fake with fictional details. The first card however, used in the Yasuda Bank in October, bore the name of one Doctor Matsui Rin and he certainly did exist. Police arrested and questioned Doctor Rin, but it was established soon after that he had a credible alibis, backed by many witnesses. This wasn’t a dead end owner, due to Matsui Rins rather keen and somewhat peculiar dedication to organisation. He explained to police that he had exchanged business cards with around 600 people and of those, only 100 were the version of the card used at the Yasuda Bank. Whenever he exchanged cards, he wrote the date, time and place of the exchange on the back of each card he received. This opened up the path for police to find a potential suspect amongst the cards held by the incredibly anal doctor. Of the 100 cards exchanged that could hold the potential suspect, 62 were quickly traced and cleared of any suspicion, whilst a further 22 cards were deemed irrelevant to the investigation as their details failed to match those described by witnesses. Police finally narrowed this search down to 14 cards which contained potential suspects.

Whilst police trailed these fourteen potential suspects, six of the bodies of the victims from the bank poisoning were sent to two different university hospitals, Tokyo University and Keio University, for analysis.  It took some time for results to return, with Keio University first to announce their finding, confirming that traces of “a cyanide compound” had been used as a poison. The results were, however, preliminary, and to further understand the nature of the compound used, would take more time. This, however, did confirm what most already knew, that poison had been administered, and so police began to theorise how the killer had administered the poison to himself and suffered no ill effects. The most convincing theory they came up with was that a harmless oil had been used in the same bottle of the poison, which would have floated upon the surface. As the pipette was dipped into the fluid, the killer would have kept the penetration shallow for his own drink, thereby sucking only harmless oil into the pipette and dipped the pipette deeper into the second layer of fluid for the bank staff, sucking up poison. As for why he had used two medicines, there were two theories, either the killer had used some kind of binary poison that remained inert until an activation substance was administered, or the first medicine was simply an inert substance to lull the staff into a sense of security when taking the second, poisonous substance.

The investigation so far had been vast and long reaching and it took police six months to simply narrow down the stack of business card owners supplied bu Doctor Matsui. In August 1948, as far as suspects went, police were finally able to make further ground, and they began zeroing in on one suspect in particular, a 56 year old local artist by the name of Sadamichi Hirasawa.

Born on February 18th, 1892, Hirasawa had moved to Otaru, Hokkaido, the Northernmost island of Japan, with his parents at the age of six. He flourished as a young artist, and by his late teens began to specialise in the Tempera style of painting, an ancient technique which utilised paint pigment mixed with egg yolk and water. By the age of 22, he was selected to exhibit work at the Nitten, a government sponsored, national Japanese art exhibition held yearly in Tokyo. His rise as an artist continued and saw him join the Japanese Watercolour painters Association and exhibit frequently in both national and local exhibitions. Two years later he married and moved to Tokyo, taking on a job as a lecturer at the Tokyo Art Academy.

The evidence that police held on Hirasawa was, some might say, tenuous at best. Foremost was the damning fact that he had been previously arrested on four occasions for fraudulently attempting to cash cheques around Tokyo, writing a fake name and address on the rear of the cheques. When Hirasawa was asked about the business card he received from Doctor Matsui, he could not supply them with it, as he claimed he had had his wallet pick-pocketed the previous summer and the card was inside at the time. Police also noted that his bank deposit book showed a deposit of 130,000 yen in the days following the Tegin robbery, around half the sum of the money stolen at the bank and lastly, and most bizarrely, Criminal Director Jiro Fujita, who headed the investigation, concluded that his family name was judged to be “suspicious”. Regardless, on 23rd August, police arrested Hirasawa at this family home in Otaru, Hokkaido, by a member fo the Tokyo Metropolitan Police and escorted by train back to Tokyo.

Police contacted the survivors of the poisoning and requested they come in to ID Hirasawa, along with 8 other witnesses, however, rather than any traditional line-up, Hirasawa was simply presented to each witness individually and asked if they recognised him as the man who had claimed to be the doctor. Of the 11 witnesses, 6 negatively ID’d him whilst the following 5 said they thought he bore a resemblance, but they could not positively or negatively ID him either way with any certainty. As for Hirasawa himself, he vehemently denied involvement, but could not explain where the money he had deposited into his bank in the days following the crime had come from. Police responded by bringing in Inspector Hachibei Hachitsuka, a member of the Metropolitan police with some renowned for previously solving a series of high profile cases. Hachitsuka did, however, have some rather unorthodox methods in his arsenal, and promptly started on a long series of interviews with Hirasawa that most would class as torture sessions. Within two days, Hirasawa protested this treatment by stealing a glass pen from a desk, slashing open his left wrist and smearing blood on the wall of his cell, writing “Innocent” in large bloody characters. A guard promptly discovered the scene and sent Hirasawa to the hospital wing, effectively saving his life and foiling his attempt at suicide. He repeated this first attempt twice more, on both the 22nd and 24th of September, by running head first into a wall, whilst screaming “I swear by heaven and earth, I am innocent!” And the second time by overdosing on medication, though both attempts similarly failed. Not he 27th September, 3 days after his third attempt at suicide, Hirasawa confessed to the Teigin poisoning and robbery, repeatedly giving oral confessions and finally a written confession on October 5th.

On the 8th October, Hirasawa was moved to the Kominato Detention Centre, where he was treated for shock before being officially charged with poisoning, robbery and also the two counts of attempted robbery from October and January prior to the Teikoku Bank incident. Due to his state of shock, however, Hirasawa appeared to later be unaware that he had signed any statement at all and further, he seemed not two be able to recall meeting with the chief prosecutor who had taken his written confession. As if this wasn’t murky enough already, his confession contained several glaring inconsistencies.

“The poison was in a bottle similar in shape to a beer bottle, I poured the substance from the bottle directly into the cups.”

Instantly the first inconsistency stands out from Sadamichi’s confession. The doctor who had been in the bank had been seen to use a glass pipette, described as one similar to those issued to medics in the Japanese Army, however, in Sadamichi’s confession, he said he had poured the poison directly into the cups. The cups too, created a second inconsistency. In his confession, Sadamichi used the Foreign loan word, “Kappu”, rather than the Japanese word for a traditional tea cup, “Chawan”. In Japan, this is not simple semantics. By using the loan word, Sadamichi was indicating that the cups used were in the style of a typical Western cup.

It was around this time that things with the Teikoku Bank incident took a sharp turn to something rather more dark indeed. Whilst Hirasawa had been undergoing torturous questioning, both Keio and Tokyo University had released there final analysis of the victims bodies from the poisoning. Shortly before Hirasawa’s confession, Keio had proposed that a chemical known as Acetone Cyanohydrin had been used as a poison, whilst later, Tokyo University claimed it to be Potassium Cyanide. The differences were vitally important, Potassium Cyanide was a common substance available throughout Japan to anyone with a mind to procure the substance, however, its effects didn’t tally with the known facts of the case. Potassium Cyanide would have likely been instantly fatal and would have caused chaos in the bank. Acetone Cyanohydrin, on the other hand, was a different matter altogether and had links with a much darker aspect of Japan, one which many people were working rather tirelessly to keep in the shadows.

Unit 731

Officially known as the “Epidemic Prevention and Water Purification Department”, Unit 731 was a Japanese Military unit headed up by General Shiro Ishii, based in Manchukuo, Modern day North East China, with a series of satellite branches, including one in Shinjuku, Tokyo. The main facility in stood on 6 square kilometres of ground, surrounded by a trench and 3 metre earthen wall, with a further 2km no-go radius that included a no-fly zone upheld even for Japanese aircraft. The facility was populated primarily by Prisoners picked up throughout the Japanese empirical territories of Manchuria, Korea, Mongolia, Russia, Malta and China, along with 3607 known Japanese who worked within Unit 731, many supplied by Universities and Medical Schools from mainland Japan. Prisoners were transported to the facility by overnight rail, which also brought in research materials for the unit to make use of.

Whilst there is no complete list of work undertaken by the staff of Unit 731, since the war details have emerged of some of the cruelest human experimentation seen amongst a war that was positively jam packed with war crimes from all sides. Code named “Maruta”, prisoners, which consisted of criminals, anti-Japanese political prisoners, homeless, handicapped and a generous helping of citizens swept up for undertaking “suspicious activities”were the subject of Vivisections, amputations, the removal of internal organs and reconfiguration of digestive systems, all naturally without any form of anaesthesia. Grenades, bombs and flamethrowers were tested on live targets to study their effects, with targets tied to stakes, hammered into the ground along with various exposure experiments that would gradually increase exposure until the subject eventually died, including X-Ray, Air Pressure, starvation, electrocution, burning, burying subjects alive and injecting them with substances such as sea water and animal blood. Prisoners had limbs and extremities dipped into ice-water to test the effects of frostbite, whilst other prisoners were forced into participating in sex acts to study the spread of syphilis. Women were routinely raped and forced to carry pregnancies, often whilst carrying some kind of fatal disease to test the effects.

One other, crucial arm of experimentation undertaken at Unit 731 included the invention and testing of biological warfare systems. “Flea bombs” used to spread Bubonic plague were devised, along with bombs that could spread typhoid, dysentry, cholera and anthrax over vast distances, whilst “clothing drops” were performed throughout unoccupied China, to spread diseases amongst the unsuspecting population. Details of a handful of the experiments were published in peer-reviewed medical journals at the time, with the experiments being claimed to have been undertaken upon “Manchurian monkeys”.

As the war came to an abrupt end, Unit 731 was hastily liquidated in an attempt to conceal the horrific history of what had been happening at the headquarters. Victims throughout the war period had been dissected and then incinerated on-site in efforts to keep the whole thing tightly centralised, and as the chaos of surrender loomed, and the Red Army strode nearer to the facilities, orders were given to destroy as much evidence as was possible. This included murdering the remaining prisoners, along with the Chinese and Manchurian labourers that worked on the site. General Ishii ordered workers to take the secret of the facility to the grave and buildings were blown up as the evacuation completed.

During the post war occupation of Japan, MacArthur struck a deal that saw the details of the experiments and any documented research traded exclusively with the Americans, who were keen to keep the Soviets in the dark, in exchange for immunity from prosecution for war crimes. Many of the head doctors that operated some of the most brutal experiments, though tracked by the Americans, went on to occupy key medical posts in both he public and private sector. The Soviets took a different tact and did manage to prosecute 12 members of staff from Unit 731, however, hundreds more dissipated back into mainland Japan under the guise of normal imperial soldiers or military staff carrying small dosages of Potassium Cyanide handed out to them by General Ishii which they were told to use if they were captured, in order to “take their secrets to the grave”.

These dosages of Potassium Cyanide might be considered highly relevant to the Teikoku case, but there is in fact, a much more substantial detail. Throughout the war, the 9th Research Institute of the Japanese Military, known as the Noborito Institute were closely linked with the development of poisons and bacterial weapons. One of the fruits of their research just so happened to be Acetone Cyanohydrin, a poison which activated several minutes after its ingestion. The problem for the Japanese authorities and anyone else attempting to keep the Japanese biological and chemical warfare programs quiet, was the fact that Acetone Cyanohydrin would have only been available to those within such programs and any mention of one program, was likely to uncover the whole, tightly knitted operation.

The Trial of Sadamichi Hirasawa

Back in the Kominato Detention Centre, Sadamichi Hirasawa was preparing to stand trial in December of 1949 for the poisoning of 12 people, the robbery of the Teikoku Bank and the attempted robbery of two more banks. Almost immediately after his confessions were taken, he had recanted them, at times explaining that he had not even remembered giving them at all. At the time in Japan, a confession, no matter the method of extraction, was admissible as evidence in court and s such, the lack of other evidence slipped by the wayside. His trial commenced on the 20th December, in the Tokyo District Court where he instantly pleaded not guilty. Sadamichi’s primary defense centered around a coerced confession, backed up with evidence of a medical condition he had suffered following an attack by a Rabid dog and the ill effects of a rabies inoculation. His doctors claimed that after the inoculation, he had fallen unconscious for three months and upon his recovery had been showing the symptoms of Korsakoff Syndrome, an amnestic disorder, characterised by bouts of amnesia and invented memories created by the memory to fill in the gaps created by the said amnesia. This he said, accounted for the four cases of him cashing fraudulent cheques in the past, because he could not judge correctly the consequence so this actions at the time.

Hirasawa also pointed out that none of his fingerprints were found at the scene, showed the court negative results of an analysis of the handwriting taken from the man who cashed the cheque the day after the incident and gave an alibis, backed up by six witnesses that he was out taking a walk at the time of the incident, though perhaps as it was in the vicinity of the bank, it was better for him that it was thrown out either way. Curiously, the poison used to kill the bank staff was referred to throughout the hearing as Potassium Cyanide and there was no mention of any doubts surrounding the substance or conflicting reports from Keio University given.

On July 24th, 1950, Sadamichi Hirasawa was found guilty and formally charged with sentence of death. On the same day, Hirasawa put forth a request for a retrial, though one year later, it was dismissed. Once again, the same day of the dismissal, a request for retrial was submitted and four years later, in 1955, it was rejected. Curiously, not a single official had stamped Hirasawa’s order for his execution, which left him suspended in limbo, unable to obtain retrial, but no closer to having his sentence of death carried out.

Throughout the 1950’s, several Japanese journalists and authors began to scrape away at the surface of the crimes undertaken by the Japanese Unit 731 during the Second World War and in 1959, Author Kiyohara Matsumoto published a book on the case titled “The Mystery of the Teikoku bank Incident”, which posited that a former member of the Japanese Unit 731 was the culprit.  It further went on to suggest that the money deposited into Hirasawa’s bank on the days following the crime was procured by the artist after he had painted and sold a pornographic painting, an act which he would have wanted to keep quiet at the time, due to the embarrassment it would cause his family and the damage it would cause to his reputation as a serious artist. 

Between May 10th 1955 – April 21st 1987, 18 further requests for retrial were submitted and denied and Hirasawa became Japans longest standing prisoner on Death Row. Still, almost 50 years after his trial had ended, not a single official had stamped the approval for his execution. After his transportation to Miyagi Prison Sendai Detention branch, which housed the equipment to execute prisoners, his sentence was still never stamped, despite the fact that that most prisoners were executed within a week of their transfer and the previous record holder for longevity lasting a mere three months.

Whilst in jail, Hirasawa had painted over 1300 paintings, with materials supplied by his supporters. At one point he was even given his own studio space in the prison that he could go to to paint away from his cell. In 1963, an exhibition was held in Tokyo that displayed his works exclusively painted throughout his imprisonment.

On April 29th, 1985, Hirasawa was moved to Hachioji Medical Prison due to his age. He was by then 93 years old and had spent 38 years in prison and two years later, on May 10th, 1987, aged 95, he passed away in Hachioji from Pneumonia. Throughout his nearly 40 years spent in jail, he maintained his innocence and not one government Justice Minister ever greenly his execution order.

Several Post-humous requests for retrial have since been submitted, in 1987, 1989 and the latest saw the 20th request for retrial submitted in 2015.

Theories & Conclusion

So who was guilty for the murder of 12 innocent Tokyo civilians in 1948? If it had been Hirasawa, why had no one signed off on his death sentence? If it was not him, then who?

Hirasawa later admitted he had painted pornographic paintings and his family members spoke of at least four that they had personally known him to have painted after the war. In 2000, several paintings attributed to Hirasawa were unearthed. Whilst the money deposited to Hirasawa’s bank in the days following the incident officially remains a mystery, it seems highly likely that Hirasawa kept it’s origins a secret to maintain face within the artistic community.

The poison used in the murders still to this day remains a mystery. It seems doubtful that it was potassium cyanide, given the delayed effect it had on the victims, however the exact compound was never confirmed. Further deepening the conspiracy, there are several that suggest that the links the universities had at the time with Unit 731 and Japans biological and chemical weapons programs, along with the ties to high society would have played a role in hamstringing the publication of the results.

If an ex-Unit 731 officer was involved with he poisoning and robbery, the details leaking out to the public would have caused a great deal of embarrassment for Japan and a great deal of trouble for America, who had struck the immunity deal to keep the information from the Soviets. In fact, various journalists from Japanese national newspapers were attempting to unravel the goings on of Unit 731 at the time of the Teikoku incident, but all found themselves pressured to drop their investigations. A reporter from the Yomiuri Shinbun named Endo was contacted directly by Jiro Fujita, the head of the investigation for the Teikoku case, who told him,

“Please stop your investigations into the incident that you are currently trying to uncover. This is a command from a top authority. It’s a complicated matter with various relationships involved, and General Ishii and his troops will not be brought down without the aid of exposure from a first class spy. Please follow this request and think of others.“

Furthermore, General Ishii, the head of Unit 731, reportedly told American interrogators at the time that he himself believed one of his men had been involved with the Teikoku Bank incident and that the method of poisoning undertaken by the criminal was an almost exact repeat of an experiment carried out at Unit 731 during the war, however, General ishii is the only person to have ever mentioned such an experiment and until then, Unit 731 had never had known, direct involvement with the administration of poisons on a large scale. During the war period, general poisons were handled by a different biological warfare division entirely, that of the Noborito Institute. Whether or not one believes Ishii is somewhat moot when considering a conspiracy, however, as it is not unthinkable that members of Unit 731 could have had contact with the poison in their programs and with the two programs being tightly linked as they were, one can easily imagine a conspiracy to cover up the true identity of the murderer regardless if they were from Unit 731, or the Noborito Institute as the discovery of one, would have likely left to the discovery of the other. In reality, Ishhii’s words only prove that the killer was a former member of Unit 731, rather than the Noborito Institute.

There are others, like journalist Haruko Yoshinaga suggest that the Teikoku case was actually an American Human Experimentation test itself, though the evidence is flimsy at best, suggesting that the poison was that of the binary kind and not a poison handled by the Japanese at the time. Yoshinaga posits that the two earlier attempts at robbery and failure were proof that these were failed experiments and goes on to conclude that they were therefore American tests of a poison they would go on to utilise in later warfare. 

At an exhibition of Hirasawa’s prison work held in Tokyo to commemorate the 70th anniversary of the case, Eizo Yamagiwa told the Japan Times,

“We have to continue making efforts to prevent memories of the case from eroding, because injustice will continue unless his innocence is proved in a retrial,”

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