The House He Would Not Leave: The Miyazawa Family Murders

Content note: this piece describes the murder of two children and their parents inside their own home, and the killer’s behavior in the hours he spent in the house afterward. If you need to skip the physical detail, the section to jump past is “The Hours He Stayed.”

The House He Would Not Leave

Listen. Almost every murder I have ever written about ends the way you would expect it to end — the killer runs. He wipes his prints, he pockets the weapon, he leaves the way he came in, he disappears down a street, he catches a bus, he burns his clothes in a bin somewhere the next morning. The whole shape of a killing, once the killing is done, is gone. Get out. Get away. Do not stay in the room where you have just ended the lives of other people, because that room is now the most dangerous place on earth for the person who made it that way.

The man who killed the Miyazawa family did not run.

He killed a six-year-old boy first, by strangling him in bed in the loft where the boy slept. He killed the boy’s father at the bottom of the stairs. He killed the boy’s mother and his eight-year-old sister in the same loft where the boy was already dead. Then he went to the kitchen. He opened the freezer. He took out four cups of ice cream and he ate all of them. He poured himself a glass of the family’s barley tea. He sat down at the family’s computer and used it. He went into the bathroom and he used the toilet and he did not flush. He had cut his hand during the attack, and the cut kept bleeding, so he opened the cabinet under the sink and he found the mother’s sanitary napkins and he bandaged himself with them. He rifled through the family’s documents and threw them into the bathtub. He stayed for six hours. He stayed for eight hours. He stayed until sometime near dawn, and then, at some point nobody has ever been able to fix, he left.

He has been gone for twenty-five years and eight months. He has never been caught.

That is the case. Everything else in this piece — the evidence, the theories, the DNA, the shoes from South Korea, the sand grains from an American desert, the sweatshirt only a hundred and thirty people in Japan ever owned — is texture on the same central impossible fact. He killed a family of four in their own house on the night of December 30, 2000, and then, instead of running, he stayed in the house with the bodies until morning. He acted like the house was already his. And then he walked out into a Tokyo winter dawn and vanished so completely that a quarter century of Japan’s largest police effort has not been able to touch him.

I want you to hold that in your chest before we go any further. Before the shoe brand, before the haplogroup, before the retired detective who has spent forty-one years on this case and the journalist who thinks the killer was a foreign soldier and the mother-in-law who lived one wall away and never heard a sound. Before all of it. Just hold that he stayed. That is the shape of the case. That is where every question in it points back to.

The Family Whose Names You Should Know

Before I tell you what happened in that house, I need to tell you who was in it. The Japanese press, for very good reason, has kept the Miyazawa family in the frame for twenty-five years — but in the English-language retellings of this case they tend to become the family, a plural noun with no interior. I am not going to do that. Their names were Mikio, Yasuko, Niina, and Rei. Say them out loud, in your kitchen, once. This is a case where the missing lives in the reader’s chest, and the reader deserves to know whose lives are missing.

Mikio Miyazawa was forty-four years old. He worked for Interbrand, a British-owned marketing and brand consultancy with an office in Tokyo. He was, by every account of him, a soft-spoken man who liked his work and loved his family and did not have enemies in the way that men in those retellings sometimes turn out to have had. There was no gambling debt. There was no affair. There was no crime boss he had crossed. There was a father who came home from the office, and a wife he loved, and two children he was watching grow up in a small two-storey house he had built with family money in a quiet residential pocket of western Tokyo. Nothing about Mikio’s life suggested it was a life somebody would come to end.

Yasuko Miyazawa was forty-one. She was a tutor — she taught children out of the family home, small groups, mostly local children whose parents wanted them ready for the entrance-exam pressure that shapes so much of Japanese childhood. Yasuko had grown up in the exact plot of land the family now lived on. Her parents’ house sat right next door, sharing a garden wall. Her mother, Haruko, was on the other side of that wall on the night the family was killed. Haruko heard nothing. She would learn what had happened to her daughter, her son-in-law, and her two grandchildren by walking across the small shared yard the next morning, wondering why nobody had answered the phone, and letting herself in.

Niina Miyazawa was eight. She was in second grade at a nearby elementary school. She was academically ahead of her class, and she loved ballet, and she was, in the way that eight-year-old girls sometimes are, the reason her mother’s face changed when she talked about her. Niina slept in the loft with her mother that night because the loft was the family’s shared sleeping space in the winter, when the downstairs got cold. She was killed lying next to her mother.

Rei Miyazawa was six. He was in kindergarten. He lived with a mental disability that the family did not describe in detail to the public, but that they treated with the ordinary devotion of parents to a child who needed a little more attention and a little more patience. Rei slept in the mezzanine level of the loft, in his own small bed, a half-story down from his mother and sister. He was killed first. He was strangled in his bed. He would not have understood what was happening to him.

I want you to hold onto that fact. He would not have understood. There is not a version of this crime where that fact does not sit at the center of it. Whatever the killer wanted, whatever the theories eventually settle on, the case begins with a man who chose to start with the smallest and most defenseless person in the house. Everything else about him — everything the DNA and the shoes and the profile and the theories try to reach toward — is downstream of that choice.

Kamisoshigaya, Winter, Late 2000

The Miyazawa family lived at 3-chōme, Kamisoshigaya (上祖師谷), Setagaya Ward, Tokyo. Setagaya is not a hard place to picture. It is one of the twenty-three special wards of central Tokyo, on the western side, quieter than Shibuya, greener than Shinjuku, largely residential, and considered a good address for a young family. Kamisoshigaya sits at Setagaya’s western edge, close to the neighboring city of Chōfu, backing onto a stretch of city green called Soshigaya Park. It is the kind of neighborhood where nothing is supposed to happen. It is the kind of neighborhood the Miyazawas chose specifically because nothing was supposed to happen there.

The family’s house was small and modern by Tokyo standards — a two-storey wooden structure with a partial loft, sharing a garden with Yasuko’s parents’ house on the same lot. December 30, 2000 was cold. Winter in Tokyo is a dry, sharp cold, and the temperature that night dropped below freezing. The family had spent the day quietly. Mikio and Yasuko had done a little year-end housework. The children had played. Niina had, at some point in the day, made a small handmade card for the new year. It would still be on the table when the police found it.

By the evening the family had settled. Some time before eleven p.m., they were all asleep upstairs. Rei was in the mezzanine level of the loft, in his own bed. Yasuko and Niina were in the loft above him. Mikio was still working downstairs at his home office computer — the last activity logged on the machine that night, before the killer sat down at the same keyboard, is from Mikio, and it stops at 10:38 p.m.

At some point between 10:38 p.m. and 11:30 p.m., a man climbed a small tree in the garden, boosted himself onto the roof, cut a screen out of the second-floor bathroom window, and lowered himself into the house.

The Night

He went to Rei first. Rei was six. Rei was asleep in the mezzanine. The killer strangled him in his own bed, with his own hands, without waking anyone else in the house.

Then he went downstairs. Mikio came up from the ground-floor office to see what the sound was — or possibly Mikio was already on his way up to bed, we do not know, the sequence there is inferred from the placement of the body — and the killer met him at the base of the staircase. There was a fight. The killer had brought his own knife into the house with him. During the struggle with Mikio, his knife broke. He went to the kitchen. He took a sashimi knife — the long thin blade Japanese cooks use for slicing raw fish — from the wooden block on the counter. He came back and he finished. Mikio died at the foot of his own staircase.

Then he went back upstairs. He killed Yasuko and Niina together in the loft, both with the sashimi knife, both while they were probably already awake and probably already terrified. This is where the fight was hardest. This is where the killer cut his own hand deeply, on his own blade, in a way that would leave blood everywhere and would become the single most important piece of physical evidence in the case. His blood, the killer’s blood, is on the walls of that room. His blood is on the tatami. His blood is on the futons. His blood is on Niina’s pillow.

And then he did something with the bodies that I want you to sit with, because it is one of the reasons Japanese investigators have never been able to agree on what kind of man he was. When he was finished with Yasuko and Niina, he covered their faces with cloth. Not Rei’s. Not Mikio’s. Only the mother and the daughter, both of whom he had brutalized far more than the other two. In Japanese criminology this specific gesture — covering the faces of victims after killing them — is treated as a hallmark of one of two things: acquaintance, meaning the killer knew the victim well enough that he could not look at what he had done; or remorse, meaning the killer knew what he had done and briefly could not bear it. It is almost never a gesture that a random panicked home-invasion killer makes. It is a gesture of someone whose relationship to the room has weight in it. That single act, more than any other, is what fuels the domestic Japanese theory that the killer knew the family — a theory the police have never officially adopted but have never officially closed either.

And then the killing stopped. Everyone in the house was dead. And the man who had done it did not leave.

The Hours He Stayed

You have to understand that this section is not a list of grotesqueries assembled to shock you. Every single object I am about to name is a piece of evidence that the Tokyo Metropolitan Police have used, and are still using, to try to identify the killer. Every one of them, on its own, would be an unusual thing for a killer to leave. Together, they form the strangest scene in modern Japanese criminal history.

He was bleeding. His right hand was open across the palm from where his own blade had turned against him. He went into the bathroom. He opened the cabinet where the family kept toiletries. He took out the mother’s sanitary napkins and he pressed them against the cut. He kept some. He used others. He left them, bloodstained, in the sink and on the floor.

He used the toilet. He did not flush. That excrement was still in the bowl when the police arrived. It has been forensically analyzed. It contained, among other things, string beans and sesame seeds — small facts about what the killer had eaten in the hours before he decided to climb a stranger’s roof.

He went to the kitchen. He opened the freezer. He took out four cups of Häagen-Dazs ice cream. He ate all four of them. He did not use a spoon — he crushed the paper cups in his hands and squeezed the ice cream directly into his mouth. Investigators have puzzled over this detail for two decades: some read it as regression, some read it as haste, some read it as the behavior of somebody who did not know how to eat that particular unfamiliar food. He then took a whole cantaloupe melon out of the fridge and ate that too. A cantaloupe melon in a Japanese fridge at year’s end is a fifty-dollar gift, the sort of thing families buy for New Year and eat carefully. He ate all of it. He drank four bottles of barley tea — mugicha, the drink most Japanese households keep chilled in the fridge year-round.

He sat at Mikio’s computer, the same computer Mikio had been working on hours earlier, and he browsed. The activity log survives, and it is one of the strangest pieces of evidence in the case. He connected to the internet. He tried to open the ticket reservation page for Gekidan Shiki (劇団四季), Japan’s largest musical-theater company — the kind of website a person in Tokyo would go to if they were thinking about booking seats for Cats or The Lion King. But the log shows something more useful than that: he did not type in Japanese anywhere. Not once. Every keystroke was mouse-navigation and browser-history clicking. He never opened the Japanese input method editor. He never wrote a single character in the country’s language. Which strongly suggests he could not — or at minimum, did not know how to on that machine. In a case where almost every piece of physical evidence is ambiguous enough to fit two or three theories, this is one of the few that points hard and single-directionally: the man who killed the Miyazawa family did not use Japanese on their computer.

He rummaged. He pulled family documents out of drawers and threw them into the bathtub. He looked in closets. He walked around a house where four dead people lay in three different rooms, and he behaved — and this is the part that has haunted every investigator ever assigned to the case — like a man for whom the presence of those four dead people made the house more his, not less. He was not spooked. He was not hurried. He was not panicked. He was at home.

Sometime between dawn and roughly 10 a.m. on December 31, 2000 — the last hour anyone can place him inside the house — he left. He left through the front door, or through the same window he came in, we do not know. He left most of what he had brought with him. His jacket. His sweatshirt. His scarf. His gloves. His hat. The waist bag around his hips. His shoes. He walked out of that house, into a cold Tokyo morning, effectively naked from the waist up, wearing no shoes, or wearing something he had taken from the family — we do not know that either.

What we do know is what he left behind. And what he left behind is, on paper, more than enough to identify almost any killer in the world. It has never been enough to identify this one.

What He Left in the House

Here is the physical evidence catalogue the Metropolitan Police published from the scene. I am giving it to you in full because I need you to feel the weight of it, and because it explains why this case has never officially gone cold. This is not a case that ran out of leads. This is a case that only has leads, and none of them have ever quite closed.

• A gray Uniqlo bucket hat, size medium.
• A white long-sleeve baseball-style shirt with purple sleeves. Only 130 of that specific shirt were ever sold in Japan — across 41 stores, between August and December 2000. Police traced 12 of the 130 buyers by name. The other 118 have never been identified.
• A plaid scarf.
• A black windbreaker jacket.
• A pair of black gloves, cotton, common household make.
• Several white handkerchiefs.
• A gray-and-black nylon waist bag — a “bum bag” or fanny pack — with an adjustable strap sized to a 70–75 cm waist. The strap gives the police the killer’s waist measurement almost to the centimeter.
• A pair of South Korean-manufactured “Slazenger”-brand sneakers, size 27.5 cm (roughly US men’s 11). That specific model of shoe was never sold in Japan. Every pair of that shoe on Japanese soil arrived either in the luggage of a traveler or through a private import.
• His blood, in significant quantity, from the hand wound — enough for full DNA extraction, full haplogroup analysis, and blood typing (Type A).
• His fingerprints on multiple surfaces in the kitchen, the bathroom, the computer keyboard, and the loft.
• His shoeprints throughout the house.
• His feces in the toilet, unflushed, forensically analyzed for dietary content.
• His hair, on the floor and on the futon.
• The sanitary napkins he used to bandage his hand.
• His saliva on the crushed ice cream cups and on the rims of the barley tea bottles.
• His internet history on Mikio’s computer — and, equally telling, the total absence of any Japanese-language input on that computer during the hours he used it.

Sit with the length of that list for a second. That is not the evidence pool of an unsolved case. That is the evidence pool of a case that should have closed inside a week. The reason it did not is a combination of three things, and I want to name all three: the killer’s DNA and fingerprints are on no Japanese database and no foreign database anyone in Tokyo has been able to compare against; the physical items he left behind trace back to points of purchase where the trail runs out at strangers who paid cash; and the most identifiable single object — those sneakers — are from a country whose forensic cooperation with Japan on this specific case has been repeatedly described by retired investigators as, at best, uneven.

The Man in the Blood

From that pool of physical evidence, a picture of the killer’s body has been reconstructed with unusual precision. He was male, Type A blood, right-handed, approximately 170 cm tall (5’6”), and slim — the waist bag’s 70–75 cm strap and the shirt sizing confirm a lean build.

His age is where the police and the science have quietly disagreed. In 2018, the Tokyo Metropolitan Police narrowed their working profile to a man aged 15 to 22 at the time of the murders, based on climbing ability, the physical fitness required to enter through the second-floor bathroom window via the tree, and clothing-size analysis. That profile, if correct, would put him at 41 to 48 today. In late 2025, however, a fresh DNA-age reanalysis published in the Japanese press estimated the killer was in his thirties at the time of the crime — which would put him at 55 to 65 today. The two estimates are incompatible, and investigators appear in recent statements to be leaning toward the older number. What that means in practice is that the man is almost certainly still alive. Whether he is a man in his mid-forties or a man in his early sixties, he is out there. He is somebody’s neighbor. He is somebody’s brother. He is, possibly, somebody’s husband. He is, possibly, somebody’s father.

The DNA analysis has also pointed, repeatedly and consistently over multiple rounds of testing across the last two decades, to something that in the Japan of 2000 would have been genuinely rare: his Y-chromosome haplogroup is one commonly seen in populations on the Korean peninsula, and his mitochondrial DNA — the DNA inherited only from the mother — shows markers most typical of Southern European populations. Which is to say: a Korean father, and a European maternal line. In practice this could mean many things, and any responsible geneticist would tell you that a haplogroup profile is not a proof of nationality — but it does tell us with a high degree of confidence that the killer was not the son of two ethnically Japanese parents, and that his ancestry likely reached, at some point on his mother’s side, into Europe.

That single genetic detail has fueled almost every theory of the case that isn’t simple robbery-gone-wrong. Because the physical evidence tells a robbery-gone-wrong story badly: there was a substantial amount of cash in the house, and it was not taken. Mikio’s wallet was not emptied. Yasuko’s jewelry was untouched. What the killer took, if he took anything, was small and hard to catalogue — a diary belonging to Yasuko, some receipts, a manila folder or two. If robbery was the motive, the killer changed his mind about it partway through and became a resident instead.

The Sand From an American Desert

There is one more piece of physical evidence from the scene that is worth its own section, because it is the strangest single detail in a case built of strange details. When investigators examined the killer’s discarded sweatshirt under a microscope, they found, embedded in its fibers, grains of sand not native to the Kanto region of Japan. The mineral composition was analyzed. The grains were traced, over the course of years of geological consultation, to sand sources associated with the American state of California and, most persistently in the reporting, with the area of Edwards Air Force Base — a US military installation in the Mojave Desert.

How grains of sand from a US Air Force base in the California desert ended up on a sweatshirt worn by a man who murdered a family in Setagaya, Tokyo, on the night of December 30, 2000, is a question nobody has ever answered. It is the reason the case has attracted, over the years, theories involving American military personnel, US-based Korean nationals with military connections, foreign hired assassins, and a range of other cross-border possibilities. Nothing has ever been proved. The sand just sits there, in the evidence file, next to everything else, as one more thing about this killer that does not fit the shape of a stranger who broke into a stranger’s house on a winter night in a residential neighborhood in Tokyo.

The Theories, and Why None of Them Has Closed

There are, broadly, four theories that have survived twenty-five years of scrutiny. I am going to lay them out roughly in the order Japanese analysts weight them today, not in the order the Western press has tended to present them.

1. The acquaintance theory (顔見知り説). The strongest domestic Japanese theory, and the one that fits the killer’s behavior better than any other. Its supporters point to a specific pattern of evidence that a stranger does not usually produce: the killer covered Yasuko’s and Niina’s faces with cloth after killing them, a gesture Japanese criminologists strongly associate with acquaintance or remorse; he moved through the house without hesitation, as though he knew the layout; he calmly bandaged his own hand wound with items from the family’s bathroom cabinet; he stayed for hours without any indication of the fear or urgency a stranger would show in an unfamiliar house; and the attack on the mother and daughter was significantly more brutal than the attacks on the father and son, which is a pattern investigators associate with personal grievance rather than random violence. The police have never publicly adopted this theory, but they have also never publicly closed it. It is what a lot of Japanese armchair investigators — and, quietly, some retired officers — believe.

2. The foreign-hitman theory (外国人説). The theory associated most publicly with Fumiya Ichihashi, a former Mainichi Shimbun investigative journalist who spent fifteen years on the case and published a book about it in 2015 — Setagaya Ikka Satsujin Jiken, from Kadokawa. Ichihashi’s argument, in short: the Korean-manufactured shoes; the DNA profile with Korean paternal ancestry; the sand from an American military installation; the specific fighting knowledge suggested by the way the killer moved through the house; the discarded professional-looking equipment; and, load-bearingly, the total absence of any Japanese-language input on Mikio’s computer during the hours the killer spent using it. All of it, Ichihashi argues, points to a former South Korean military man — possibly Special Forces — who came to Japan on a contract killing, executed it in a way that spiraled from a robbery-cover into a family massacre, and returned home. Ichihashi is a serious journalist and his theory is not fringe. Another domestic true-crime writer, Ippei Ichikawa (一橋文哉), has covered the case across multiple books and reaches a similar conclusion — that the killer was operating in a professional capacity that went beyond ordinary criminal robbery. The theory is not, however, accepted by the police. The most decorated retired investigator on the case, Takeshi Tsuchida — the former head of the Seijo Police Station’s special investigation task force, who worked the case for forty-one years and has continued to work it privately in retirement — has called Ichihashi’s conclusion, on the public record, “one hundred per cent nonsense.” His reasons are technical and detailed. He believes the killer was Japanese, or long-resident in Japan, and that the physical evidence has been misread. Two serious men, two incompatible readings of the same body of evidence, and the case sits in between them.

3. The random-intruder theory. A stranger chose the house because it was accessible — the tree by the bathroom window was climbable, the neighborhood was quiet on New Year’s Eve — killed the family in a panic that spiraled out of control, and then, in what may have been shock or dissociation, failed to leave. This is the theory the Tokyo Metropolitan Police have officially worked from for most of the twenty-five years, largely because it is the theory with the fewest specific commitments. It fits the physical evidence. It does not fit the behavior. Random panicked intruders do not sit down and eat four cups of ice cream and a whole cantaloupe melon. They do not calmly cover their victims’ faces. They do not stay until dawn.

4. The targeted-family theory. Someone specifically wanted the Miyazawas dead — for reasons connected either to Mikio’s work, or to Mikio’s public campaign to have a local skate park closed (skateboarders had confronted him more than once in the months before the murders, and residue analysis of the killer’s clothing has intermittently been read as consistent with skate-park material), or to a business dispute involving Yasuko’s brother-in-law who lived next door with her parents. None of these leads has ever produced a suspect who matches the physical evidence. This is the theory the Miyazawa family, in their own quiet way, have never fully dismissed.

None of these theories has produced a suspect who has been arrested, questioned, and released — let alone charged. There have been persons of interest over the years, briefly. There have been tips that felt live for a week or a month and then dissolved. The current lead investigator, Manabu Ide, superintendent of the Special Investigation Task Force, works with thirty-five detectives still officially assigned to the case as of 2026. They have interviewed nearly a quarter of a million people. They have followed more than sixteen thousand tips. They have not found him.

What Happens to a Case That Never Closes

In 2010, the Japanese government did something that made the Miyazawa case, on paper, prosecutable forever. It abolished the statute of limitations on murder. Before 2010, a Japanese murder case had to be closed within fifteen years or the killer, even if identified, could no longer be tried. After 2010, that clock is gone. If the man who killed Mikio, Yasuko, Niina, and Rei is identified at seventy-five, he will be tried. If he is identified on his deathbed, he will be tried. The state has committed itself, formally and permanently, to keeping this case open.

In 2019, after nineteen years of preserving the family home exactly as investigators had left it — the blood on the tatami, the sanitary napkins, the shoes, the sand grains — the Tokyo Metropolitan Police agreed to a request from the family to demolish the house. It had become, over the years, an object of increasingly disturbing attention from true-crime tourists, some of whom had tried to enter it. Setsuko Miyazawa, Mikio’s mother, had been maintaining the family shrine there. When the demolition finally happened, she saved what she could from the small garden the family had planted.

In late 2025, on the twenty-fifth anniversary of the murders, the Metropolitan Police renewed their public appeal. The reward on the case, which has been offered since 2007, currently sits at 20 million yen — roughly $130,000, USD. It is the largest reward ever attached by the Japanese state to an unsolved crime. Alongside the reward, in December 2025, the Japan Stone Industry Association joined the appeal — because a new round of forensic analysis of the granular residue on the killer’s discarded sweatshirt had suggested that some of the material was stone dust of the kind used in cutting engravings into small stone figures. The industry association asked its member stonemasons to look at their records and to look at their memories. Forty-five tips came in over the following weeks. One of them flagged that the engraving style on a small roadside Jizō statue — a Buddhist protector figure that Japanese families place at crossroads — carried marks similar to those the killer’s equipment might have produced. That lead is, as of this writing, still being worked.

In August of 2026, twenty-five years and eight months after he left the Miyazawa house at dawn, the man who killed the family is somewhere between his mid-forties and his mid-sixties, depending on which of the two competing age estimates you believe. His fingerprints have been on file since New Year’s Eve 2000. His DNA has been on file since New Year’s Eve 2000. His blood type has been on file since New Year’s Eve 2000. His shoe size, his waist size, his height, his handedness, the fact that he does not read or write Japanese, the way he covered the faces of the mother and daughter he killed, and his food preferences from the twelve hours before he committed the murders have been on file since New Year’s Eve 2000. What has not been on file, in all of that time, is his name.

The Grandmother Next Door

I want to end with the woman who found them.

Yasuko’s mother, Haruko, lived one wall away. When the family had built their little two-storey house on the same plot as her own, she had thought of it as a gift — the daughter she loved, the son-in-law she liked, the grandchildren she could see from her kitchen window, all of them one door away for the rest of her life. That is the whole point of families on shared land. That is why the Miyazawas were there.

On the morning of December 31, 2000, Haruko woke up in the house next door to a killer. He was still inside, at that hour, still walking through her daughter’s kitchen, still using her son-in-law’s computer. She did not know. There is nothing in the record that suggests she heard anything at all through the shared wall on the night of the murders. She got up. She made her morning tea. She noticed, some time before 10 a.m., that she could not hear the children next door and that the family had not answered the phone. She walked across the garden. She let herself in.

She found Mikio at the base of the stairs first. She went upstairs. She found her daughter and her granddaughter in the loft. She found her grandson in his bed. She was, at that moment, a woman who had lost her entire family in a single house on a single night while she slept a few metres away from them and heard nothing.

I have thought about Haruko a lot while writing this. Not because there is anything more to say about what she did — she called the police, she survived, she has stayed largely out of the press for twenty-five years the way Japanese families in this position tend to — but because the shape of what happened to her is, in some way, the shape of the whole case. He came into the family’s house. He killed the family in it. And he lived in it while she slept, and while the neighborhood slept, and while the year turned. He was inside their walls, using their things, eating their food, bleeding onto their tatami. And in that house, that whole long night, he was safe. He was safer inside a house of four people he had just killed than any random man in Tokyo would have been sitting alone on a park bench. He knew that. He acted on it. He stayed.

Whoever he is, wherever he is now, he is a man who chose to stay in a house he had just filled with dead children. That is the fact you have to hold about him. Everything else — the theories, the haplogroups, the sand, the shoes, the sanitary napkins — is texture on that fact. The Metropolitan Police still want him. The reward is still there. If you speak Japanese and you happen to know a man in his late fifties or early sixties with a scar across his right palm that has been there since New Year’s Eve 2000, the tip line for the Setagaya case is 03-3482-0110, at the Seijo Police Station, and it has been answered every day of every year since it was set up.

Somebody, somewhere, knows him. He is not a ghost. He ate four cups of ice cream and used a family’s bathroom and slept in a stranger’s house for hours after killing them, and then he walked out into a Tokyo morning and became the neighbor of somebody who has not, in twenty-five years, put together the shape of what she or he is looking at. This piece is, in the smallest possible way, an ask to that person, wherever they are, to look again. Say their names one more time before you put this down. Mikio. Yasuko. Niina. Rei. They were a family. They lived in a house in Setagaya. Somebody killed them, and stayed the night, and left at dawn, and has not been found. Please do not forget them.

Sources

• Tokyo Metropolitan Police Department (警視庁), Special Investigation Reward System designation and public appeal materials, Seijo Police Station.
• Kyōdō News (共同通信), 多くの物証残るも姿見えぬ犯人 世田谷一家殺害25年 (December 2025).
• Fumiya Ichihashi (市橋文彌), 世田谷一家殺人事件, Kadokawa, 2015.
• Ippei Ichikawa (一橋文哉), long-form Japanese true-crime coverage of the Setagaya case across multiple books and periodical pieces.
• Takumi Inoue, 世田谷一家殺害事件における犯人像の多角的分析と未解決要因の学術的考察 (Note.com longform analysis, 2024–25).
• Japan Today, “Setagaya family murders remain unsolved after 25 years,” December 2025.
• Japan Today, “New book claims to shed light on Setagaya family murders,” December 2015.
• Tokyo Reporter, “Setagaya family murders: DNA is hope for solving case 25 years later,” 2025.
• ABC News (Australia), “The faceless killer who slaughtered an entire family and then vanished for two decades,” December 2019.
• MSN Japan / independent Japanese press reporting, DNA reanalysis and estimated-age findings, December 2025.
• Nikkei, retrospective on the case, 2025.
• Tokyo Weekender, “On This Day in Japan: The Setagaya Family Murder Case.”

If you have any information about the Setagaya family murder case, the Tokyo Metropolitan Police tip line remains active at 03-3482-0110. The reward for information leading to the identification and arrest of the perpetrator stands at 20 million yen (approximately $130,000 USD).