The killing at school
On June 1, 2004, Satomi Mitarai, a 12-year-old sixth-grade pupil, was killed during the school day at Okubo Elementary School in Sasebo. Contemporary reporting identified the child responsible as an 11-year-old female classmate. A utility-style paper cutter was involved. This page does not reproduce descriptions of Satomi's injuries because they add no value to understanding the investigation or legal outcome.
The killing drew intense attention in Japan because both the victim and the child responsible were elementary-school pupils. Satomi's age, the school setting and the youth of the other child also meant that ordinary adult criminal-law labels could easily misstate what happened procedurally.
Why this was not an adult criminal prosecution
The 11-year-old was below Japan's age of criminal responsibility. The matter therefore moved through juvenile and child-welfare procedures rather than an adult criminal trial that could end in a conventional criminal conviction and prison sentence. Contemporary Family Court reporting described the proceeding as a juvenile hearing and focused on treatment, assessment and protective measures.
That distinction is essential to this archive's status label. The case is not classified as “convicted / adjudicated” because no adult criminal conviction occurred. It is classified Solved / Legal Disposition: responsibility was identified and a formal Family Court disposition followed.
Psychological assessment
On June 14, 2004, the Sasebo branch of the Nagasaki Family Court opened a juvenile hearing and ordered a psychological or psychiatric assessment. Contemporary Japanese reporting noted that such an assessment for a child under 14 was unusual. The purpose was not to decide adult criminal responsibility, but to help the court understand the child's condition and determine an appropriate protective response.
Investigators and contemporary reporting discussed conflict between the girls, including online exchanges. Those accounts should not be flattened into a single definitive “motive.” The final court process was concerned with the child's conduct, development and treatment needs as well as the act itself.
The September 2004 protective disposition
On September 15, 2004, the Sasebo branch of the Nagasaki Family Court ordered the girl sent to a child self-reliance support facility. The court also authorized compulsory measures restricting her freedom for up to two years when required for treatment or safety. Contemporary Japanese reports described the duration and the child's age as exceptional.
This was a protective juvenile disposition, not a sentence for murder in an adult criminal court. Describing it as a prison sentence, or describing the child as a criminally convicted murderer, would be legally inaccurate.
Protecting a child's identity
After the case, internet users circulated a purported identity and a nickname for the 11-year-old. Crime by Region does not reproduce either. They are unnecessary to document Satomi's death, the official response or the Family Court disposition, and repeating them would undermine the privacy principles appropriate to a child offender.
The archive also avoids turning the case into internet folklore. The documented victim is Satomi Mitarai. The documented institutional outcome is the Family Court's protective placement and authorized compulsory measures. Those facts are sufficient to tell the case accurately.
Timeline
June 1, 2004: Satomi Mitarai, 12, is killed at Okubo Elementary School in Sasebo by an 11-year-old classmate.
June 14, 2004: the Sasebo branch of the Nagasaki Family Court holds a juvenile hearing and orders a psychological assessment.
September 15, 2004: the Family Court orders placement in a child self-reliance support facility and permits compulsory measures for up to two years.
Current classification
The Murder of Satomi Mitarai is classified Solved / Legal Disposition. The child responsible was identified, but she was 11 and below the age of criminal responsibility. The legally documented outcome was a Family Court protective disposition, not a criminal conviction. This case file deliberately preserves that distinction.