The Setagaya Family Murder (12/31/2000) - Background

The Setagaya family murders occurred on December 30, 2000, in Tokyo, Japan, where the Miyazawa family was brutally killed. Despite extensive investigations, the case remains unsolved. https://en.m.wikipedia.org/wiki/Setagaya_family_murder

Key findings include:

• Military Connection: Sand found in the killer's belongings was traced to the area around Edwards Air Force Base in California, suggesting a possible link to U.S. military locations.

• Acquaintance with the Family: No definitive evidence indicates the killer knew the Miyazawa family personally.

• Age of the Killer: Investigations estimate the killer was between 15 and 35 years old at the time of the murders. The killer left behind substantial amounts of DNA and fingerprint evidence at the crime scene, and the notable absence of the killer’s DNA and fingerprints from existing databases, combined with certain fingerprinting requirements for adults that existed at the time, has led some to theorize that the killer was a minor at the time of the incident.

• Current Status: As of June 24, 2025, the killer's identity and status remain unknown.

In 2022, a 7 episode podcast called “Faceless” was released which dove deeply into the Setagaya murder case. It included ample primary sources and research and explored 6 plausible theories surrounding the case. The podcast won the 2023 New York Festivals Radio Awards—Bronze Medal for Best Documentary Podcast and a 2023 Webby’s Best Crime & Justice Podcast Honoree*. In my opinion, the podcast contains some of the most accurate and up to date information on the case. The author, Nic Obregon, spent 2 years researching the case for the podcast, and appears to have remained invested in the case since.

Resolution criteria

Because this is an unsolved murder case, and one that has remained unsolved for a long time, bettors should be aware that many of these answers may not resolve for a really long time. As such, percentages should reflect the market’s overall degree of belief that a given statement question is true, irrespective of the likelihood that it will actually resolve.

Resolutions will not be done willy nilly, and given the long-term nature of the market, if there is any uncertainty I will probably lean towards keeping the market open rather than making a hasty resolution. Official sources will be used for resolutions. I may also consider other options like N/A’ing or resolving to a specific percentage under certain circumstances.

Feel free to add additional relevant questions of interest.

Clarifications

A “direct military connection” means that at the time of the incident, the killer either 1) served/was serving in the military or 2) had immediate family (parents, spouse, siblings) in the military.

A similar standard will be used for the question about “direct connection to local, national, or international politics.” Politics, in this context, can be extended to include legislators, foreign diplomats, and local law enforcement, but largely excludes members of the military (except perhaps in the case of high-ranking military officials whose roles are directly intertwined with politics).

The killer “knew” the family if it is determined that at the time of the murder, the killer would have recognized at least one of the family members from somewhere. This statement may be inferred, such as if the killing was determined to be targeted or if the killer was a local resident in the same neighborhood as the Miyazawa’s.

For the “minor” question, just a note that the age of adulthood in 2000 varied by country (e.g. it was 18 in the US but 20 in Japan and South Korea). The killer will need to have been a minor in whatever jurisdiction they resided in.