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UNSOLVED: The Murder of the Miyazawa Family

Despite a mountain of evidence, we may never get answers in the slaying of an innocent Japanese family.

An outside view of the Miyazawa home in Setagaya.
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  • Photo Credit: Wikimedia Commons

It was the year 2000, and in the hours that stretched between December 30th and December 31st, an indescribable atrocity came to the Tokyo suburb of Setagaya.

The Miyazawas lived here, a typical middle-class family consisting of a father, Mikio, a mother, Yasuko, a daughter, Niina, and a son, Rei

But in these late hours on the New Year's Eve holiday, a home invasion resulted in the slaughter of the entire family—a crime that remains unsolved to this day.

The Murder of the Miyazawa Family

On the morning of December 31st, Yasuko's mother, Haruko, stopped by the Miyazawa house to check on her family after her phone calls to the house didn't go through.

What she found inside the home was a gruesome discovery. Mikio, Yasuko, and eight-year-old Niina had been stabbed to death. Six-year-old Rei had been strangled.

When investigators from the Tokyo Metropolitan Police Department arrived on the scene, they determined that the intruder had gained entry through an open window in the second-floor bathroom. They had to have climbed a tree to access the window and removed the screen themselves.

Investigators also concluded that the family had been murdered in the night between 11:30 pm and 12:05 am. Young Rei was the first to die, and perished at the killer's bare hands while he was sleeping in his second-floor bedroom. Mikio heard a scuffle and rushed upstairs to his son's room, where he fought and injured the assailant.

Unfortunately, the killer got the best of him, stabbing him in the head with a sashimi bōchō knife and even breaking off a piece of the blade inside his skull.

The killer then moved on to attack Tasuko and Niina with the broken knife. However, it was a Santoku knife owned by the Miyazawa's that killed them.

Oddly enough, it appeared that the killer remained in the house for several hours after the crime. For anywhere from 2 to 10 hours, the killer apparently used the family's computer, drank four bottles of barley tea, ate some melon and ice cream, used the restroom (without flushing), and took a nap on the couch.

The killer had also ransacked some drawers, dumping some of the contents into the bath and the toilet. Some money was stolen, but not all of it.

Even stranger, the killer left behind a pile of items on the couch, including the knife, a scarf, a hip bag, a sweater, a jacket, a hat, gloves, shoes, and two handkerchiefs.

Odd Happenings Leading Up the the Miyazawa Murders

The Miyazawa home was an interesting house in an interesting neighborhood. The house was more like a duplex, with Yasuko's mother, sister, and brother-in-law living next door in the connected unit.

Behind this house was Soshigaya Park, which, at the time, had pending expansions. Because of this, many of the families in the area had moved out of the area.

What was once a community of more than 200 families was narrowed down to four. The neighborhood was essentially a ghost town.

In the weeks leading up to the tragic murder, some odd and unfortunate instances occurred around the neighborhood. In the skate park nearest to the Miyazawa home, some teenagers were causing a commotion and disturbing the family.

Mikio confronted these kids, demanding they respect the family's peace.

A witness reported that, around the same time, Mikio was involved with another confrontation, this time with a group of young individuals that belonged to the Bosozoku, a Japanese motorcycle gang.

It also appears that, since the summer months, there were unsettling incidents of animal harm in the area. Rats had been killed and stray cats were tortured and mutilated.

A week before the murders, Yasuko had mentioned to her father-in-law that an unfamiliar car had been sitting outside their home. This wasn't a one-off event, but an occurrence that had happened several times, despite the fact that there was nearby parking.

Who Killed the Miyazawa Family?

Despite a hefty amount of DNA and personal belongings left behind at the scene, the police have been unable to make an arrest in the case. Though they have been able to uncover some potentially helpful and specific clues as to the killer's identity.

Thanks to the killer's use of the Miyazawa's toilet, investigators know that the perpetrator consumed string beans and sesame seeds the day before the murder. The clothes and knives left behind were traced back and determined to be purchased in Kanagawa Prefecture.

In fact, only 130 units of the sweaters left in the Miyazawa were made and distributed. Unfortunately, the police could only locate a dozen people who bought one.

Small amounts of sand were discovered in the killer's abandoned hip bag. Lab analysis determined the sand to be from two locations: a Japanese skate part and a Nevada desert. The shoes left at the scene were made in South Korea, yet marketed by the British company Slazenger.

None of the DNA and fingerprints found in the how yielded any results in the police database, which indicated the killer did not have a criminal record. In place of a name, investigators devised a profile of what the killer might look like: roughly 5'5" tall with a slim build, between the ages of 15 and 35 at the time of the crime, and likely right-handed.

What the police did learn from the blood left behind was that it was Type A, which did not belong to the Miyazawa family. Further analysis also determined the killer to be a male, possibly of mixed race.

The DNA implied a maternal lineage from Europe and a paternal lineage from East Asia.

As there's a mountain of evidence and no suspect, it almost seems as though the killer is a ghost. But some amateur sleuths on the internet have some theories of their own.

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.

A second popular theory asserts that the killer was a traveling vagrant relying on the train system to evade capture. The Miyazawa home was close to several convenient train lines, and shortly after the crime, an anonymous injured man sought care at a train station medical center.

The Latest in the Miyazawa Family Murder Case

The investigation into the Miyazawa family murders, also known as the Setagaya family murder, is one of the largest conducted in Japanese history. More than 246,044 investigators were involved, and they collected more than 12,545 pieces of evidence.

All of the evidence remains in police custody, and the TMPD has never given up on the case. As of 2019, reports declared 35 officers were still investigating the case full-time. Each year the police return to the Miyazawa house and conduct memorial ceremonies.

There is still a ¥20 million reward for any information that might lead investigators to an arrest. Anyone who knows any information regarding the case should call 03-3482-3829.