The Saitama Dog Lover Serial Disappearances is an investigation into people who vanished after becoming associated with dog breeder Gen Sekine near Kumagaya. A renewed inquiry connected a decade-old series of disappearances to Sekine, but the eventual closure did not settle how many people had been killed. In Jake Adelstein’s account, the case turns on the recovery of forgotten leads, the precarious exchange of information among police and underworld sources, and a scoop lost just before the arrests.

Background and rediscovery

By the time the case reached Adelstein, Sekine was suspected of being a serial killer with some form of yakuza connection: he was described as a yakuza, an ex-yakuza, or a yakuza affiliate. Several people associated with him had disappeared over the preceding ten years. Saitama police had investigated the first three disappearances, but the leads dried up and the original case was largely forgotten.

The disappearance of Akio Kawasaki, president of a waste management company, brought the old pattern back into view. After Kawasaki failed to return home for several days, his wife went to the police. Officers initially asked routine questions about his behavior, home life, and possible enemies. Her answers did not point to an obvious explanation. But when she mentioned that her husband had disagreed with a dog breeder, the officer in charge became grave and warned her to prepare for the worst if Kawasaki had been involved with Sekine. A missing-person inquiry had suddenly acquired a suspect and a history.

In January, Adelstein and Yamamoto were in the office when a police source known as the Cobra brought them the case, insisting that the information was highly confidential. Adelstein’s reporting focus had shifted to organized crime, theft, and public security; the emerging investigation brought those concerns together. By the end of January, the Yomiuri team had assembled a working picture of four missing people believed to have been killed: Kawasaki, a housewife, a yakuza boss, and his driver. The suspected connection was clearer than the motives, which investigators and reporters still could not establish.

Leads, intermediaries, and a changing case

The investigation advanced through information passed between police, reporters, and underworld figures, rather than through a single decisive discovery. A source told Adelstein that Sekine’s situation might involve an internal power struggle, but presented that as a guess, not a demonstrated motive. The distinction matters: the case generated theories before it yielded proof, and access to people who might know more did not guarantee that their information could immediately be used.

When Adelstein passed what he had learned to a source, that person contacted Takada. Takada had Sekine in his hands and invited the source to listen to his questioning, but the source declined, telling him not to kill Sekine and asking to hear what the questioning revealed. This exchange shows how the inquiry depended on personal assurances as well as official investigation. The source’s refusal did not end the cooperation; Takada gave his word, and the source relied on it.

Arai’s revelations then redirected the investigation. He had not participated in the disappearances of the last four victims, but his driver, Shima, had. Arai had learned from Shima that Sekine poisoned Endo and his driver, Wakui, and that Shima helped bury them. That account made Shima the crucial witness: what he knew could implicate Sekine. Police arrested Arai on a fraud charge, expecting that his information about Shima would be more useful than a confession to a much older murder that would be difficult to prove without a body.

The route from Arai to Shima was complicated by the existence of tapes. On the day Arai was arrested, the Consigliere told Takada about them. Takada immediately contacted Shima and demanded that he reveal where Endo’s body was, threatening that Shima himself would otherwise need a burial place. For a time, the investigation stalled. Sekiguchi left the team in November, and the unspoken assumption was that Shima had been killed and the case would remain unsolved.

Arrests and the case’s closure

Takada continued pursuing Shima. In late November, he tracked him down after Shima had changed his name and married, then passed the information to Sekiguchi, who reported it to Saitama police. Shima was arrested in December. Confronted with the existence of the tapes, he cooperated. The police searched a site in Gunma Prefecture that Shima identified and found enough of Kawasaki’s teeth to support their case. The search was conducted by a small team, without the Yomiuri or other outside observers knowing about it.

On January 5, after the New Year’s holidays, Saitama police released Shima on bail and announced the arrest of Gen Sekine and his wife, Hiroko, for the dismemberment of Kawasaki. Sekine admitted almost everything within hours of his arrest. After an investigation that had occupied a year and reached back, in one sense, more than a decade, police declared the Saitama Dog Lover Serial Disappearances case closed.

Closure did not mean that Adelstein obtained the scoop. The Yomiuri team had planned to withhold publication until just before Sekine’s arrest, but that plan had already fallen apart. Adelstein later understood that he had missed an opportunity by failing to keep close watch on the open case over the holidays and by not giving Sekiguchi his home phone number. The source had risked calling the office, but Adelstein was not in a position to act on the information in time. The case’s resolution therefore brought both an investigative conclusion and a professional failure: he knew the plan and had a strong lead, yet did not report the decisive discovery first.

What remained unknown

Sekine and his wife were convicted of murdering four people. That number defines the proven outcome, not necessarily the full extent of the crimes. How many people they actually murdered remains a mystery. The gap between the suspected disappearances, the evidence recovered, and the four murders established in court prevents the case’s official closure from serving as a complete accounting of its victims.