How Japan's Biggest Murder Investigation Changed the Country Forever

Theory, young American Military member went awol

My guess is that the killer was a youngun between the ages of 16-23, based on his clothes. Also i think that none of the DNA matched because the killer could be a minor or something or their DNA was just not taken at any point

Correction: In 2000, Japan had virtually no specific statutory laws governing DNA collection, meaning there were no explicit legal bans regarding minors in criminal investigations. So the skaters DNA definitely was tested.

Obviously its korean military and family was killed for the project because the mother delayed moving out. The odd behavior of the perpetrator just points out that he hate japanese people because of the war, the fact that he beat the child even after death, ate their food, used their computer, took a sh.t in their home after killing them and left without flushing is signs of pure hate and despising. Also, he was confidant and left all the evidence because he knew he was nowhere registered. The fact that police asked for fingerprint data and was told none actually adds up to it. I think the sand is just for confusion since it belong to a military base in US. From the very beginning I had a hunch it was whoever was behind that project.

You can't be seriously thinking it was the teenage skater. The police obviously checked their DNA. Besides judges approved warrant on a probable cause to take DNA from a minor, the police are allowed to take discarded items such as cigarettes, spit, saliva from used snack wraps or water bottles or soda can etc etc. They could just wait for the teenagers to throw some item in the garbage and take it and most likely did it. I can only make 2 things out of this, either it was korean military or its just a bs story cover up.

"Family next door"(A neighbour) then investigate the fucking neighbours who have 13 year old kid !!! Fuck this police man

Even when the skaters were suspects, no investigation against them.... Suspicious
Even After all the evidence being present it's a clear case of corruption and power as much as I can see

I got that all Asian countries have pathetic justice and investigation systems. Killer must be those skateboarders, military people dont eat ice-cream that way and leave toilet like this. They are very disciplined.

Can you add multi-language audio support to your videos? Its Youtube's new feature. Please add support for Hindi language.

This sounds like someone they knew.

This murder is so disturbing. I don’t know how it’s still considered unsolved knowing the number of evidence that was left at the scene. Especially with the blood, I think you would’ve been able to get DNA from it and it would reveal the identity of the killer and the case would be solved years later with the advanced technology we now have. I think it’s very possible that a young teen could’ve done it, maybe the teen who wrote the post on 5chan. It’s very bizarre that the killer was in the house for a few hours after committing the murders. It’s like he didn’t know what to do and was hanging around the house until he figured out what he was gonna do. Kind of like what a young kid would do after something very bad a,d freaking out. I wonder if it could’ve been someone who knew the family since the killer strangled Rei and he was the only one to have died in such a way and left him in his bed as if he was sleeping. It could’ve been a sense of remorse and he couldn’t stand what he just did.

The answer is in the DNA.

So basically they know who it is & don’t want to arrest them.

I can't believe that u could just walk away with murder like that

Imagine having a statute of limitations on MURDER. What theeee...??!

it’s crazy that there weren’t any CCTVs or cameras around. And since it happened right during peak season, you’d think someone would have noticed or witnessed something, but nope nothing.

Creo que si las prendas encontradas como pertenecientes al asesino, tengan origen en dos países, es por qué al menos hubo dos complicaciones, como si el motivo era un robo, pero al encuentrar a la familia se asustaron y la menor grito, luego una pelea con el padre entre dos, pues es práctica imposible que un hombre de menos de 60 kg derrote a un hombre de 87 kg, además de cuatro personas

El hecho que dejó todas las pruebas posibles, nos da a entender que o bien es un narcisista con un nivel de necesidad de atención que tuvo que asesinar a toda una familia, o un retrogrado con un intelecto menor a 80, además de psicópata; pero definitivamente el objetivo de los asesinatos era la hija menor, así que si es pedófilo con doble nacionalidad, posiblemente de escasos recursos, pues comió de la nevera no se llevó nada, por qué el motivo era secuestrar a la niña, pero quizás incluso sufre de trastorno de la personalidad, pues recordemos que para estar tres horas en la casa, utilizo la luz, además de que incluso es muy posible que es un adolescente pues comió el helado antes de todo o un adulto no mayor a 25 años

im really not trying to be disrespectful, that fit at 10:28 kinda hard tho

they should make an exception to their privacy law, the guy murdered an entire family FFS. Bend the rules just this one time and work in partnership with the US and interpol. using DNA databases, using 2026 technology and modern investigations techniques (whole‑genome sequencing, forensic genealogy, proteomics, as well as re-examining all the evidence with modern tools), you'll eventually catch the guy

this case is ideal for genetic genealogy; does Japan authorities have access to such data for this type of analysis? Not sure if family DNA testing is used much in Japan :(

surely, this case could be solved in this age we live in with all the DNA evidence. If the theory that the perpetrator was a minor at the time, wouldn't it's fingerprints be available now? I agree with a lot of the comments that it's probably the child of influential people who have used their money to keep people quiet. I really hope there will be justice, the poor grandmother has had to live with this for decades.

You are sharing and you are still not sure, I’ve seen other people explaining so it’s better if you are sure about that the killer did instead of saying not sure or what other people say.

Oh I'm so upset.

What if the evidence are also some kind of his plan?
I mean something like from a belonging of someone he kīlled
U can use anything to avoid everything
U just need to know how to use

11:52 danggg feces can determine what you are??? Crazyy

the killer probably isn’t south korean, it's more likely to be north considering north korean has to be the most strict and more rubble country than south

idk, my gut tells me the killer must be vvvip's son or relatives.

issues with skateboarders (motive), grip tape found in bag (only skaters carry this), ice cream and leaving so much evidence (definitely not a hitman, probably a kid), youthful clothes and agile (young), sand was found in the area between LA and bakersfield (an area directly in between two massive skateboarding hubs, places an avid skater would visit)
probably a kid of japanese and american (hence connection to region) parents and but probably live in japan. evaded fingerprints due to being a minor

After reading some theories here I go for the option it was her student who also happened to be a child of a military person.

He was an animator, who, created faces of cats to look like humans...He made a comment of a likeness between a man and one of his animations, probably in a restaurant, that's why the killing of the cats began in the park...The wife connecting the two sought out the man in the restaurant to apologise, and the husband was annoyed because he saw the danger...The killer looked for any receipts in the wife's bag, and the drawer to seek any connection to the restaurant....The computer was accessed by the killer, looking for the cat likenesses......

It’s 2026, run genealogy dna tests. Screw the privacy law. This heinous crime needs to be solved and the psychopath given the harshest punishment.

After learning about the Setagaya family massacre online recently, I was deeply saddened and hope the case can be solved soon so that the perpetrators will pay the price.
I believe the difficulties in the Setagaya case lie in three aspects.
First, the DNA and fingerprint databases are relatively limited. While Japanese people value privacy, this may be somewhat excessive. In the future, collecting DNA and fingerprints from all citizens and all foreigners entering and leaving the country could help deter crime.
Second, it is necessary to accelerate the comprehensive coverage of surveillance cameras and reduce blind spots, so that criminals will be less likely to commit crimes.
Third, a strong sense of faith among the population is important, as people with genuine beliefs are generally less likely to commit crimes.
In fact, every country in the world has unsolved cases, and these three aspects need to be addressed. By improving these areas, the chances of catching criminals will be greatly increased, and faith in particular may also help reduce the occurrence of crime.

Still think about this case almost weekly.

I can’t believe there’s no answers even with so much DNA

You can almost be certain that this would not have been the killer's first time doing this nor would it have been his last.

Have they or can they try the genetic genealogy on this case? They collected so many DNA why they didnt try it

Why don’t they run the prints in the us again

Check the US fingerprint database

11:37 i just bipped right on the highway

It really does sound like it was a kid. Everything about what happened after the murders: dumping documents into the tub, not flushing the toilet, whipping blood all over the place, eating the ice cream like a squeeze pop. It all comes across like a kid acting out their impulsive thoughts, doing all the things their mother wouldn’t let them do at home (including, you know, killing people). They were probably familiar with the family but only in passing (since they didn’t kill the mother-in-law next door). I think either it was a kid in the area who frequented the skate park, or a former student (or someone who knew a student) at the cram school the mother ran. I don’t think the attack was especially personal, I think it was targeted more at an idea this family (and the act itself) represented to them than the family themselves.
Either way, may the victims rest in peace and their families find the justice they are looking for.

why they not checking dna/finger prints evidence in US database?

Definitely an American. They love to do some horrific murders. True crime entertainment almost exclusively exists thanks to Americans, so chances are given the evidence, it was most likely yet another American.

Amend that personal protection law, it must have exceptions for criminal cases and other related issues

He left the trace of his DNA everywhere means he knew that no one was ever gonna find my DNA . That's insane information.