Japan - Miyazawa family of 4 murdered, Setagaya, Tokyo, 30 Dec 2000 #4

[Charlot123]

<modsnip: Quoted post was edited to correct Rei's age>

While it is true that both Kohei and Rei had a different treatment (so to say...), the circumstances seem very different: being the first killed, Rei was strangled seemingly to preserve the element of surprise (the killer's alleged entry point was just next to his bedroom) while the others were killed with the knife, starting from the second victim Mikio: an adult male (aka the biggest threat in the house), while the two women were not "finished" by the killer right away thus also explaining a rising escalation in violence IMHO (get down the ladder with the adrenaline pumping, go to the kitchen, take another knife, go back and see them still alive at the bottom of the ladder, etc.)

Kohei, on the other hand, was left untouched but we could also speculate Yasufuku Kumiko wanted to kill him as well but couldn't bring herself to do it after killing Namiko (because she was wounded? Because she also has a child? We don't know).

About Mikio meeting an insanely jealous person.
Although the police also made it clear the Miyazawa's past was looked into thoroughly and nothing out of the ordinary came out, one could argue that the Nagoya case also didn't have anything out of place so it's anyone's guess if the TMPD really ruled out everyone.

There is also the certainty the killer of the Miyazawa was a male and was also young (not older than 30 years old according to the yet to be confirmed reports of this summer) so it appears very difficult to be related to jealousy: if he was 15 as per the initial report there is simply no way to explain the age gap, while if he really was 30 it's still a stretch but no so hard I suppose?

Before the unconfirmed reports of this summer, the killer's age window was reported as 15-24 years old.

On the other hand, absolutely possible that a younger/more immature person might harbor feelings that could lead to a disproportionate reaction such as this.

We know that the Miyazawa’s killer was a male. It rules out Yasufuku; plus, Satoru’s personality (strong and competitive) is very different from that of Mikio, IMHO.

The killer brought the knife with him, so he “came prepared”. He planned to kill them all, however, however…

Sometimes I wonder if he enjoyed (*killing the way he did it with Rei*) and came for the hedonistic pleasure of murdering Rei,

He did not leave the other inhabitants alive because otherwise they could have later guessed who did it.

So I do wonder if the connection (or the attraction) was Rei/(less likely, both young children), and maybe the meeting with Rei was recent or became regular enough. So had the adults survived, they’d remember the killer meeting with Rei and at least include his name in the list of suspects.

So perhaps to look through all Rei’s contacts (the clinic he was taken into for the diagnosis, or speech therapy, or some other places he visited with dad…or maybe he was invited to birthdays? Or Niina had play dates with friends and he was taken with her?) would be worthwhile? Maybe Rei had a nanny who’d bring her own son to the house?

He might have attacked Rei first because he could not deny himself that feeling.

 

[Sillybilly]

Sorry folks .. I had forgotten that there was in fact some DNA analysis in this case and it showed the perp as male.

I shall crawl back into my cave

 

[Charlot123]

Sorry folks .. I had forgotten that there was in fact some DNA analysis in this case and it showed the perp as male.

I shall crawl back into my cave

You have reminded about Rei’s death being different. It is important. Many other facts about this case might be surprising when we read about them, but could end up being “red herrings”.

Rei stands out. This hasn’t changed over the years.

 

[SHADOWW7]

I'm not taking any side — just asking out of curiosity.

I’ve noticed many people link the Setagaya killer to a U.S. military background, mostly because of the DNA hints. But I’m trying to understand the reasoning beyond that.

From what we publicly know, the killer’s behavior — staying in the house for hours, eating ice cream, using the computer, leaving so much forensic evidence, taking almost nothing valuable, and escaping in borrowed clothes — doesn’t seem like something a trained military professional would normally do during or after a violent crime.

Another thing I’m confused about:
Why would a military person target a completely random family?
The Miyazawas had no known connection to the military, no political links, and nothing high-value was stolen that would make sense as a motive. So I’m wondering what supports this angle besides the DNA markers.

For those who’ve followed the case far longer than I have:

What specific behavior, evidence, or case details (apart from DNA) make the military theory seem plausible?
Is there an aspect I might be overlooking?

Just asking to learn — not trying to dismiss anyone’s theory.
Really appreciate the experience and knowledge people here share.

 

[Eliver]

I'm not taking any side — just asking out of curiosity.

I’ve noticed many people link the Setagaya killer to a U.S. military background, mostly because of the DNA hints. But I’m trying to understand the reasoning beyond that.

From what we publicly know, the killer’s behavior — staying in the house for hours, eating ice cream, using the computer, leaving so much forensic evidence, taking almost nothing valuable, and escaping in borrowed clothes — doesn’t seem like something a trained military professional would normally do during or after a violent crime.

Another thing I’m confused about:
Why would a military person target a completely random family?
The Miyazawas had no known connection to the military, no political links, and nothing high-value was stolen that would make sense as a motive. So I’m wondering what supports this angle besides the DNA markers.

For those who’ve followed the case far longer than I have:

What specific behavior, evidence, or case details (apart from DNA) make the military theory seem plausible?
Is there an aspect I might be overlooking?

Just asking to learn — not trying to dismiss anyone’s theory.
Really appreciate the experience and knowledge people here share.

The theory is not that the killer himself is a professional military, but rather the son a of military that had ties to Yokota Air Base.

It would be very difficult to summarize everything but there are many circumstances discussed in the threads that align very well with this profile (in this thread alone I think one thing that was discussed pages ago is the fact the Interbrand - aka Mikio's company - was right where a US-Japan controlled hotel for US military families still is).

This is just one example on top of my mind but there are countless other things. Just to say two more than I can think of:

- It would so easily explain how the killer might have left the country right after the murder by using an in-base flight.
- There are some things suggesting Mikio and Rei were into airplanes (discussed in thread 2 or perhaps 3) and that they might have even visited Yokota Air Base during Friendship Day.

Again, there are many other circumstances outside the above.

Also, interesting to note that Yokota Air Base is the one and only subject the Tokyo Police categorically and absolutely refuses to comment about, while on other things they have said things among the lines of: "we cannot share information" or just "this has been ruled out".

 

[SHADOWW7]

The theory is not that the killer himself is a professional military, but rather the son a of military that had ties to Yokota Air Base.

It would be very difficult to summarize everything but there are many circumstances discussed in the threads that align very well with this profile (in this thread alone I think one thing that was discussed pages ago is the fact the Interbrand - aka Mikio's company - was right where a US-Japan controlled hotel for US military families still is).

This is just one example on top of my mind but there are countless other things. Just to say two more than I can think of:

- It would so easily explain how the killer might have left the country right after the murder by using an in-base flight.
- There are some things suggesting Mikio and Rei were into airplanes (discussed in thread 2 or perhaps 3) and that they might have even visited Yokota Air Base during Friendship Day.

Again, there are many other circumstances outside the above.

Also, interesting to note that Yokota Air Base is the one and only subject the Tokyo Police categorically and absolutely refuses to comment about, while on other things they have said things among the lines of: "we cannot share information" or just "this has been ruled out".

Thank you for explaining all this — it really helped me understand the context better. I think I get your points now.

I just have one more curiosity, and I’m asking this very respectfully:
even if the killer was connected to a military family or somehow linked to Yokota, why the Miyazawa family specifically?
That part still feels unclear to me. Were they just a completely random target he picked by chance and then escaped using the flight access? Or is there any theory that explains why this family and not someone else?

Again, I don’t mean this in a challenging way — I’m still new , and your explanations have already cleared up a lot for me. Thank you for taking the time to share the details.

 

[Eliver]

Thank you for explaining all this — it really helped me understand the context better. I think I get your points now.

I just have one more curiosity, and I’m asking this very respectfully:
even if the killer was connected to a military family or somehow linked to Yokota, why the Miyazawa family specifically?
That part still feels unclear to me. Were they just a completely random target he picked by chance and then escaped using the flight access? Or is there any theory that explains why this family and not someone else?

Again, I don’t mean this in a challenging way — I’m still new , and your explanations have already cleared up a lot for me. Thank you for taking the time to share the details.

Ultimately there is no definitive theory and no motive has ever surfaced.

They could have been targeted randomly (I don't personally think so), the family might have "meant" something for the killer (what I personally believe), or there might have been an interaction that triggered the murder (also plausible imho).

Until the culprit is caught, no one knows really.

 

[dotr]

I'm not taking any side — just asking out of curiosity.

I’ve noticed many people link the Setagaya killer to a U.S. military background, mostly because of the DNA hints. But I’m trying to understand the reasoning beyond that.

From what we publicly know, the killer’s behavior — staying in the house for hours, eating ice cream, using the computer, leaving so much forensic evidence, taking almost nothing valuable, and escaping in borrowed clothes — doesn’t seem like something a trained military professional would normally do during or after a violent crime.

Another thing I’m confused about:
Why would a military person target a completely random family?
The Miyazawas had no known connection to the military, no political links, and nothing high-value was stolen that would make sense as a motive. So I’m wondering what supports this angle besides the DNA markers.

For those who’ve followed the case far longer than I have:

What specific behavior, evidence, or case details (apart from DNA) make the military theory seem plausible?
Is there an aspect I might be overlooking?

Just asking to learn — not trying to dismiss anyone’s theory.
Really appreciate the experience and knowledge people here share.

Welcome to Ws @SHADOWW7!
One of the reasons for speculation concerning an airbase, is because of the grains of sand in the perp's bag, imo.

2024 rbbm.

UNSOLVED: The Murder of the Miyazawa Family

On New Year's Eve in 2000, the Miyazawa family was brutally murdered by an unknown assailant.

the-line-up.com

''One theory asserts that the killer is a member of the military. The sand found in the hip bag hails from an area close to the Edwards Air Force Base near Los Angeles, and Japan has had a large US military presence for quite some time.''

 

[Incoherent]

IIRC Mikio designed plane liveries as part of his job at Interbrand, which took him and the family international. There were plane calendars and models all around the house with one calendar featuring US war planes. The Yokota base nearby also had friendship days where the general Japanese public were allowed on base (still continue to this day) to get up close and view the planes, etc. Wouldn’t be beyond the realms of possibility it was visited either for leisure or work, or if not had some connection beyond the theory of the killer.

Worth noting re: the independent DNA report about the perp being in his 30’s, the official TMPD site on the case has not been updated since December 16th 2024 and still details him as being between teenage and early 20’s leading a student lifestyle. You’d think if this discovery of him actually being in his 30’s were concrete that would all be updated by now, but the TMPD’s reasoning and methods have often been more far-fetched than this.

Watch me eat my hat during the yearly December update this year when they suddenly decide to confirm it. We’ll see.

 

[you betcha]

Welcome to Ws @SHADOWW7!
One of the reasons for speculation concerning an airbase, is because of the grains of sand in the perp's bag, imo.

2024 rbbm.

UNSOLVED: The Murder of the Miyazawa Family

On New Year's Eve in 2000, the Miyazawa family was brutally murdered by an unknown assailant.

the-line-up.com

''One theory asserts that the killer is a member of the military. The sand found in the hip bag hails from an area close to the Edwards Air Force Base near Los Angeles, and Japan has had a large US military presence for quite some time.''

The sand in the hip bag interests me. I've been reading these threads for a while, but I don't remember-- did anyone ever discuss how the sand got there? It could give some hints as to his personality and hobbies. Changed his sandy shoes and put them in there? Sand stuck to the legs of a collapsible camera tripod?

 

[Incoherent]

We had a screenshot somewhere before of an aerial view over Edwards that showed a lot of the surrounding sand blown onto the base, particularly where the tennis courts were. The killer just so happened to be wearing tennis sneakers. There are also large tennis courts next to the Miyazawa house.

 

[RobertCatesby]

I just learned about this case recently, some of these details are just shocking that this guy is still free. I have two possibilities that are pretty far fetched but I would be interested to hear what you guys think:

1. JJD. Same Stealthy home-invasion style assault he was quite familiar with, and would explain the Edwards AFB sand. Inactive for quite some time and he started getting bored because he made his final call the following year in 2001. Maybe vacationed to Tokyo and figured to do one more big assault where no one would tie it to his previous activities. The DNA Mountain is the complete opposite of his meticulousness, but maybe he figured it wouldn't matter that far away.

2. Mamoru Takuma. Out of jail and working as a taxi driver at the time, maybe in the area for that. Had the sadism, emotional fragility, and compulsiveness that this would have taken. Could have gotten in some petty dispute with Mikio years earlier or online and that was all it took.

That being said, I still think the far more likely explanation is either a local teen with serious mental/psychotic issues or somebody from the Philippines or Korea working at a nearby Military base. I hope they can figure out something soon, once they get to the 25 year mark.

 

[Lalalacasbah]

I just learned about this case recently, some of these details are just shocking that this guy is still free. I have two possibilities that are pretty far fetched but I would be interested to hear what you guys think:

1. JJD. Same Stealthy home-invasion style assault he was quite familiar with, and would explain the Edwards AFB sand. Inactive for quite some time and he started getting bored because he made his final call the following year in 2001. Maybe vacationed to Tokyo and figured to do one more big assault where no one would tie it to his previous activities. The DNA Mountain is the complete opposite of his meticulousness, but maybe he figured it wouldn't matter that far away.

2. Mamoru Takuma. Out of jail and working as a taxi driver at the time, maybe in the area for that. Had the sadism, emotional fragility, and compulsiveness that this would have taken. Could have gotten in some petty dispute with Mikio years earlier or online and that was all it took.

That being said, I still think the far more likely explanation is either a local teen with serious mental/psychotic issues or somebody from the Philippines or Korea working at a nearby Military base. I hope they can figure out something soon, once they get to the 25 year mark.

Thanks for posting! I had to figure out who JJD stood for and google Mamoru lol.... I'm no expert on this case but thoughts come to mind:

1. JJD: Would a man his age and size (from what I gather in photos) at the time be able to scale up that wall and potentially crawl through the small window? I think someone very agile and smaller frame could do that not sure about his age/size! Maybe I'm wrong. Would he know enough about Japanese culture about the DNA and do we know he even was there? I don't know much about JJD so sorry if these are lame questions haha

2. Mamoru: Interesting.... I can see where you'd make the connection from the little I've read so far. I will go down that rabbit hole a bit as haven't heard of him so don't know much. Via Wikipedia, I'll try to find a better link so paraphrasing known facts I think ok to do here: fantasizing about stabbing father to death, spent time at the Japan Air Self Defense Force however discharged, etc. Only think is - wouldn't his DNA be linked to this crime by now or before? I can't remember all the legalities about Japan and DNA though!

All MOO JMO

 

[Eliver]

I just learned about this case recently, some of these details are just shocking that this guy is still free. I have two possibilities that are pretty far fetched but I would be interested to hear what you guys think:

1. JJD. Same Stealthy home-invasion style assault he was quite familiar with, and would explain the Edwards AFB sand. Inactive for quite some time and he started getting bored because he made his final call the following year in 2001. Maybe vacationed to Tokyo and figured to do one more big assault where no one would tie it to his previous activities. The DNA Mountain is the complete opposite of his meticulousness, but maybe he figured it wouldn't matter that far away.

2. Mamoru Takuma. Out of jail and working as a taxi driver at the time, maybe in the area for that. Had the sadism, emotional fragility, and compulsiveness that this would have taken. Could have gotten in some petty dispute with Mikio years earlier or online and that was all it took.

That being said, I still think the far more likely explanation is either a local teen with serious mental/psychotic issues or somebody from the Philippines or Korea working at a nearby Military base. I hope they can figure out something soon, once they get to the 25 year mark.

Cannot be either of them because they are convicted criminals for which we know their respective DNA/fingerprints and the actual Miyazawa killer's DNA has no match in any database (including Interpol).

That being said, like you I agree with the teen/son of military theory.

 

[SteveL]

We had a screenshot somewhere before of an aerial view over Edwards that showed a lot of the surrounding sand blown onto the base, particularly where the tennis courts were. The killer just so happened to be wearing tennis sneakers. There are also large tennis courts next to the Miyazawa house.

Onizuka Park - Edwards A.F.B. Tennis Courts in Lancaster, CA | Tennis Maps

Tennis courts at Onizuka Park - Edwards A.F.B. in Lancaster, CA on an interactive map of all places to play tennis and tournaments.

www.tennismaps.com

I was the one who located the courts. Also of note, the courts are named after Ellison Onizuka, the first person of Japanese ancestry to reach space. I still wonder if that fact has any relevance.

As a tennis player myself, I think the sand got caught on a ball, and he placed the ball in the hip sack.

Of the top of my head, I believe it was also discussed that sand from Misawa also turned up. <modsnip>

 

[acutename]

The sand in the hip bag interests me. I've been reading these threads for a while, but I don't remember-- did anyone ever discuss how the sand got there? It could give some hints as to his personality and hobbies. Changed his sandy shoes and put them in there? Sand stuck to the legs of a collapsible camera tripod?

would not need to be that complicated- put an open bag down during a windy day and sand gets in it- sand gets in everything at the beach. IMO

 

[Incoherent]

Could anybody more familiar comment on the content of this article?

It is in Japanese but what it says is that the killer’s Y-STR chromosome was DNA tested in an attempt to find a match to a distant relative, as it’s passed down from father to son. According to the article the probability of finding a match amongst Japanese males is 1 in 1,000. However it says that the killer’s has been tested against over 2,000 samples in Japan and no match has been found. It then insinuates that due to this the likelihood of the killer being Japanese has been lowered again.

I am not knowledgeable on this topic at all but can explain what the article itself says. Is there anyone that can shed more insight on this?

 

[Frankie Hellis]

Could anybody more familiar comment on the content of this article?

It is in Japanese but what it says is that the killer’s Y-STR chromosome was DNA tested in an attempt to find a match to a distant relative, as it’s passed down from father to son. According to the article the probability of finding a match amongst Japanese males is 1 in 1,000. However it says that the killer’s has been tested against over 2,000 samples in Japan and no match has been found. It then insinuates that due to this the likelihood of the killer being Japanese has been lowered again.

I am not knowledgeable on this topic at all but can explain what the article itself says. Is there anyone that can shed more insight on this?

I can, to some degree. Only men get the Y chromosome; women do not have one. This means, like you stated, it is passed down from male to male only. In forensic investigative genetic genealogy, a Y match helps to identify a perpetrator of a crime or unidentified human remains. Getting a match on the Y chromosome, even a distant match seriously narrows that line of searching, as it includes only male relatives.

The thing is that FIGG compares to reference testers - those who have uploaded their DNA profile to GEDmatch or FamilytreeDNA, for example. I do not think this is a common practice in Japan, so there would be few profiles to which to compare. For comparison, GEDmatch has over 2 million individual DNA profiles in their system. That they checked against 2,000 samples in Japan is virtually nothing. Especially if the guy could be American, they really need to SNP test and do forensic investigative genetic genealogy. It’s just that it against Japan’s laws, apparently.

 

[Eliver]

Very interesting

I can, to some degree. Only men get the Y chromosome; women do not have one. This means, like you stated, it is passed down from male to male only. In forensic investigative genetic genealogy, a Y match helps to identify a perpetrator of a crime or unidentified human remains. Getting a match on the Y chromosome, even a distant match seriously narrows that line of searching, as it includes only male relatives.

The thing is that FIGG compares to reference testers - those who have uploaded their DNA profile to GEDmatch or FamilytreeDNA, for example. I do not think this is a common practice in Japan, so there would be few profiles to which to compare. For comparison, GEDmatch has over 2 million individual DNA profiles in their system. That they checked against 2,000 samples in Japan is virtually nothing. Especially if the guy could be American, they really need to SNP test and do forensic investigative genetic genealogy. It’s just that it against Japan’s laws, apparently.

Very interesting.
Thank you for this insight.

 

[Charlot123]

Onizuka Park - Edwards A.F.B. Tennis Courts in Lancaster, CA | Tennis Maps

Tennis courts at Onizuka Park - Edwards A.F.B. in Lancaster, CA on an interactive map of all places to play tennis and tournaments.

www.tennismaps.com

I was the one who located the courts. Also of note, the courts are named after Ellison Onizuka, the first person of Japanese ancestry to reach space. I still wonder if that fact has any relevance.

As a tennis player myself, I think the sand got caught on a ball, and he placed the ball in the hip sack.

Of the top of my head, I believe it was also discussed that sand from Misawa also turned up. The main POI many of us share was on the tennis team there.

Would the tennis ball fit into the hip sack? More of a question as I remember the hip sack was rather flat.

There are people who walk around with tennis balls used for training hands and forearms.