In the years following Japan's deadliest postwar mass killing — the 2016 stabbing of 19 people with intellectual disabilities at a Sagamihara care facility — a young man named Kazuaki has spent years sitting across from the perpetrator, notebook in hand, searching not for a monster but for a mirror. What he found was not a coherent ideology but a familiar human wound: loneliness, invisibility, and a desperate hunger to matter. His quiet vigil at the site each anniversary is a reminder that societies do not only fail victims in the moment of violence — they often fail perpetrators long before,
A Decade After Sagamihara Massacre, Young Japanese Seek Lessons in Killer's Psychology
Satoshi Uematsu stabbed 19 residents with intellectual disabilities to death and injured 26 others at Tsukui Yamayuri En care facility in July 2016.
Even if they never kill anyone, another Uematsu could be anywhere.
Mark
Why did Kazuaki decide to visit Uematsu in the first place? What made him different from other people who just watched the news and moved on?
Mimi
He saw Uematsu smiling on camera and couldn't reconcile that image with what he had done. It created a kind of cognitive itch he couldn't scratch. When he found out that ordinary people could visit, he decided to try to understand the person behind the act.
Luke
But we should be careful here—Kazuaki was fourteen when this happened. He's now twenty-one, looking back on visits he made as a teenager. How much of his interpretation is his own analysis versus what Uematsu was deliberately performing for him?
Mimi
That's fair. Uematsu was clearly conscious of how he was being perceived. He told Kazuaki he had cosmetic surgery partly so people would take him seriously. So yes, there's a performance happening.
Mark
What did Uematsu actually say about why he did it?
Mimi
He gave different answers to different people. To Kazuaki, he talked about ideology—that people with disabilities were burdens. But to Sasaki, when asked directly, he said: "I wanted attention."
Luke
So we have two different explanations from the same person. One is ideological, one is psychological. How do we know which one is true, or if both are true?
Mimi
Maybe they're not separate. Maybe the ideology was the framework he used to justify a need for recognition that came from somewhere deeper—his loneliness, his sense of worthlessness.
Mark
Do Kazuaki and Sasaki think Uematsu was mentally ill, or just isolated?
Mimi
They don't use that language. They focus on isolation, low self-esteem, and a desire for recognition. Sasaki says what struck him most was Uematsu's "profound loneliness."
Luke
But that's a diagnosis too, just a social one rather than a psychiatric one. And we should note: Uematsu has repeatedly sought a retrial. He hasn't accepted his sentence or shown sustained remorse.
Mark
So what are Kazuaki and Sasaki actually trying to accomplish by keeping this alive?
Mimi
They're asking what society could have done differently. Not to excuse Uematsu, but to prevent the next person from reaching that point.
Le Pouls
- A university student who was fourteen when Satoshi Uematsu killed 19 disabled residents in their sleep felt compelled to visit him in detention four times, convinced that understanding the 'why' was a moral obligation the public was avoiding.
- What emerged from those thirty-minute sessions was not a coherent manifesto but a portrait of a man obsessed with appearance, starved for recognition, and convinced that an online audience validated his worldview.
- Uematsu's own words — 'I wanted attention' and 'if I had been given a chance to succeed, I wouldn't have done it' — reframed the attack not as ideological certainty but as the violence of someone who felt he had nothing left to lose and no one watching.
- A social welfare academic who also corresponded with Uematsu identified the same root: profound isolation, including the sting of never being thanked for the care work he performed at the very facility he later attacked.
- Now 21, Kazuaki warns that the conditions that produced Uematsu — online echo chambers, discrimination against minorities, unaddressed loneliness — have not disappeared, and that the next perpetrator may already be forming in plain sight.
- Both men are urging younger generations to treat this case not as a closed chapter of evil but as an ongoing question about what societies owe to people who feel unseen before they turn that invisibility into harm.
In the years following Japan's deadliest postwar mass killing — the 2016 stabbing of 19 people with intellectual disabilities at a Sagamihara care facility — a young man named Kazuaki has spent years sitting across from the perpetrator, notebook in hand, searching not for a monster but for a mirror. What he found was not a coherent ideology but a familiar human wound: loneliness, invisibility, and a desperate hunger to matter. His quiet vigil at the site each anniversary is a reminder that societies do not only fail victims in the moment of violence — they often fail perpetrators long before, in ways that go unexamined until it is too late.
When Kazuaki was fourteen, he watched Satoshi Uematsu being led away by police on television — blonde hair, composed expression — after killing 19 people with intellectual disabilities at a care facility in Sagamihara. The gap between the scale of the violence and the ordinariness of the man never left him. Years later, he discovered that visits to Uematsu in detention were possible, wrote a letter, and received a reply.
Over eighteen months, Kazuaki made four visits, each about thirty minutes, notebook ready. Uematsu explained his eugenic reasoning in flat, mechanical terms — that people with severe disabilities were burdens who should be euthanized. But what struck Kazuaki more was something stranger: Uematsu was consumed by his appearance. He had undergone cosmetic surgery, dyed his hair blonde after seeing Donald Trump, and when asked why he had smiled for cameras at his arrest, explained that he had laughed at the absurdity of looking bad in front of so many lenses. 'If I looked ugly,' he said, 'no one would take what I said seriously.'
Beneath the ideology, Kazuaki found a man whose entire sense of worth rested on appearance and perceived usefulness. In one visit, Uematsu said that if he had been given talent and opportunity, he would never have committed the crime. At their final meeting, he showed a flicker of doubt — 'maybe what I did wasn't right' — before reverting to discriminatory rhetoric once the trial began.
Takashi Sasaki, a social welfare academic whose own son has developmental disabilities, also visited Uematsu and received a simpler answer when he asked directly why the attack happened: 'I wanted attention.' Sasaki came to believe that isolation was the deeper engine — Uematsu had worked at the very facility he attacked and said no one ever thanked him for helping residents. 'What stayed with me most,' Sasaki said, 'was his profound loneliness.'
Now 21, Kazuaki still holds that notebook and returns to the care facility each year on the anniversary to lay flowers, visits that have connected him with people with disabilities and their supporters. He worries the questions raised by the killings are fading along with the memory of them. He sees the same dynamics — online radicalization, discrimination against minorities, unaddressed isolation — still present in Japanese society. 'Even if they never kill anyone,' he said, 'another Uematsu could be anywhere.' Both he and Sasaki believe the answer lies in sustained reflection, especially among those too young to remember — treating the case not as a story of evil concluded, but as a warning still unfolding.
Ten years after Satoshi Uematsu walked into a care home outside Tokyo and killed 19 people with intellectual disabilities in their sleep, a university student named Kazuaki sat across an acrylic partition from him in a detention facility in Yokohama, trying to understand how someone could do such a thing and then smile about it.
Kazuaki was fourteen when the attack happened in July 2016 at Tsukui Yamayuri En in Sagamihara, Kanagawa Prefecture. He saw Uematsu on television news—blonde hair, composed expression—being led away by police, and something about that image stuck with him. The disconnect between the scale of the violence and the ordinariness of the man committing it gnawed at him. When he later read a magazine article about someone who had visited Uematsu in detention, Kazuaki realized it was possible. He looked up the procedures, wrote a letter, and Uematsu wrote back.
Over eighteen months, before Uematsu's trial ended in a death sentence, Kazuaki made four visits. Each lasted about thirty minutes. He came prepared with questions written in a notebook, and Uematsu answered them in a flat, almost mechanical way. The killer explained his reasoning: people with intellectual disabilities who could not communicate were burdens, unnecessary, and should be euthanized if their families consented. Kazuaki found the logic absurd, full of leaps and contradictions. But what struck him more was something else entirely. Uematsu was preoccupied with how he looked. He had undergone cosmetic surgery on his eyes and nose. He had dyed his hair blonde after seeing Donald Trump. He spoke with pride about his body, built through training. When Kazuaki asked why he had smiled for the cameras as he was being taken to prosecutors, Uematsu said he had just woken up and thought he looked terrible. He had tried to cover his face but laughed when he saw the mass of cameras. "If I looked ugly when I was arrested, no one would take what I said seriously," he told Kazuaki.
The young man came away convinced that beneath the ideology lay something more human and more fragile: a man with profound low self-esteem who had placed all his value on appearance and ability. During one visit, Uematsu said something that crystallized this for Kazuaki: "I thought that even someone like me could help society if I acted on what I believed was right. There are plenty of people online who agree with my ideas." He added, "If I had talent and had been given a chance to succeed, I wouldn't have committed the crime." At their final meeting, about a month before trial, Uematsu showed what Kazuaki interpreted as his first moment of doubt: "Maybe what I did wasn't right." But when the trial began, he returned to his discriminatory rhetoric about people with disabilities.
Takashi Sasaki, an assistant to the president of Tokyo University of Social Welfare and the father of a son with developmental disabilities, also corresponded with and visited Uematsu. When Sasaki asked directly why Uematsu had carried out the attack, the answer was simpler and more revealing than any ideology: "I wanted attention." Sasaki, too, came to believe that a hunger for recognition and a deep sense of isolation had driven the violence. Uematsu had told him that when he worked at the care home, no one thanked him even when he helped residents. "What stayed with me most was his profound loneliness," Sasaki said.
Now twenty-one, Kazuaki still keeps that notebook filled with Uematsu's words and behavior. Since high school, he has visited the care facility each year on the anniversary of the attack to lay flowers. Those visits have connected him with people with disabilities and those who support them. He worries that as the memory of the killings fades, the broader questions they raised are being forgotten too. He sees parallels in the discrimination that persists against minorities—foreign nationals, sexual minorities—particularly online. "There are many issues in society that can't simply be reduced to whether one side is good or bad," he said. "Even if they never kill anyone, another Uematsu could be anywhere."
Sasaki has been asking a different but related question: What can society do to prevent resentment and isolation from turning into violence against vulnerable people? Both men believe the answer lies in sustained reflection, particularly among younger generations who did not live through the attack. Kazuaki's mission is to keep the case alive not as a story of evil, but as a warning about what happens when loneliness, low self-worth, and a desire for recognition go unaddressed in a person who has access to an ideology that validates harm.
Citations marquantes
I wanted attention.— Satoshi Uematsu, when asked directly by Takashi Sasaki why he carried out the attack
What stayed with me most was his profound loneliness.— Takashi Sasaki, reflecting on his visits with Uematsu
Envie de l'histoire complète ?
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