Gen Sekine was a dog breeder from Kumagaya, in the north of Saitama Prefecture, north of Tokyo. In 1993 four people died in a run of killings that the courts later tied to him and to his former wife, Hiroko Kazama. The deaths fell on three separate dates between April and August of that year: one in April, two on the night of July 21, and one on August 26. Sekine and Kazama were arrested in January 1995, both were sentenced to death in 2001, and the Supreme Court made the sentences final in June 2009. Sekine died in the Tokyo Detention House on March 27, 2017, at the age of 75, without having been executed.
The case turned on a trial in which the two defendants each admitted some involvement and blamed the other, and in which the judges relied heavily on the account of a third man, a former associate who had gone to the police.
Sekine was born in 1942 in Chichibu, a city in western Saitama Prefecture. He was involved early in breeding and pet businesses, and he became a breeder of real skill. In 1982 he opened a dog-breeding and sales business in Kumagaya, and it became the center of his working life and of the events that followed. He had been married several times before; his marriage to Kazama was his seventh.
Hiroko Kazama came into that business as a customer. She visited in early 1983, they became close, and they married in October 1983, when Sekine was 41. Kazama handled the accounts and also bred dogs, and she was his right hand in the business, while Sekine dealt with clients. The couple divorced on paper in 1992 but went on living and working together.
In January 1995 he was 53 and was known as a breeder of expensive dogs.
The courts found that four people died in 1993 in three separate events, and tied the deaths to money disputes arising from the business.
The first death came in April 1993. The victim was a 39-year-old man, a customer of the business, who had paid 11 million yen for two dogs. He is known by the initial K. The courts treated this killing differently from the other three: the first-instance court found that Sekine and Kazama had acted jointly in the three killings other than his.
The second and third deaths came on the night of July 21, 1993. The victims were a man aged 51 and a 21-year-old man who was with him. They are known only by initials, E and W.
The fourth death came on August 26, 1993, about five weeks later. The victim was a 54-year-old woman from Gyoda, a town near Kumagaya. She is known only by the initial S.
Taken together, the four deaths occurred on three dates: April 1993, July 21, 1993, and August 26, 1993. They were separate events, separated by weeks, and the court dealt with them as four counts of murder.
The case could not have been prosecuted without a man who had worked in the business and who went to the police in December 1994. He is known by the initial Y, and he had been a director of the business in name. His statements led to the arrest of Sekine and Kazama the following month. He had gone to the police because he feared for his own life.
He was tried separately. He was sentenced to three years' imprisonment, and by the time of the first-instance judgment in 2001 he had served the term and been released.
Sekine and Kazama were arrested on January 5, 1995, in Saitama Prefecture. By January 11, 1995, Sekine had admitted killing one former customer, and police were questioning him about others. Both of them were indicted on four counts.
Press attention to the case was heavy in the months before the arrests, following a similar case in Osaka the year before. The Great Hanshin earthquake struck soon after the arrests and drew public attention away from the case.
The trial opened at the Urawa District Court on July 7, 1995. It ran for five years and eight months. Both defendants admitted that they had some part in the events but each named the other as the one in charge, and both argued that the third man had carried out the killings himself.
The court gave its judgment on March 21, 2001. It accepted the prosecution case in large part, and its findings leaned heavily on the testimony of the third man. It found that Sekine and Kazama had acted jointly in the three killings other than the first, the one in April, and it sentenced both of them to death.
Both defendants appealed. At the Tokyo High Court they repeated the arguments made at trial, and on July 11, 2005 the court dismissed the appeals. The High Court found the account of the third man credible, noting that he had no stake in the victims and no motive to kill them.
The Supreme Court dismissed the final appeals on June 5, 2009, and the death sentences became final. The court described the killings as planned, found no mitigating motive, held that the defendants' explanations were not reasonable and showed no sincere remorse, and agreed with the lower courts that death was the appropriate sentence.
After June 2009 Sekine was held as a condemned prisoner at the Tokyo Detention House. In November 2016 he collapsed there.
Sekine died on Monday, March 27, 2017, at the Tokyo Detention House, aged 75. Kazama, then 60, remained under sentence of death.
Kazama has continued to say that she was wrongly convicted. She filed petitions for a retrial in 2012 and in 2016, and both were dismissed. A third petition was filed in 2020. In April 2025 the petition was pending at the Saitama District Court; she was 68 and held in Tokyo. The outcome of that petition is not on record.
The two defendants blamed each other at trial, and each also argued that the third man had carried out the killings. The courts did not accept either argument. The first-instance court and the High Court found the account of the third man credible, and the Supreme Court upheld the sentences.
The court found a joint conspiracy in three of the four killings. The April killing is the one that was not found to have been joint; how the court divided responsibility for it is not on record.
Sekine has also been linked to other deaths, among them a 1984 matter involving three people and a death in Chichibu. None of these was charged, no court made a finding on any of them, and they are not part of the four convictions.
1942: Sekine is born in Chichibu, Saitama Prefecture.
1982: He opens a dog-breeding business in Kumagaya.
October 1983: He marries Hiroko Kazama.
1992: The couple divorce on paper and go on living together.
April 1993: A 39-year-old customer of the business dies.
July 21, 1993: Two men die on the same night.
August 26, 1993: A 54-year-old woman of Gyoda dies.
December 1994: A former associate goes to the police.
January 5, 1995: Sekine and Kazama are arrested.
July 7, 1995: Their trial opens at the Urawa District Court.
March 21, 2001: Both are sentenced to death.
July 11, 2005: The Tokyo High Court dismisses their appeals.
June 5, 2009: The Supreme Court dismisses the final appeals; the sentences are final.
2012 and 2016: Kazama files two retrial petitions; both are dismissed.
November 2016: Sekine collapses at the Tokyo Detention House.
March 27, 2017: Sekine dies at the Tokyo Detention House, aged 75.
2020: Kazama files a third retrial petition.
April 2025: Kazama's petition is pending at the Saitama District Court.