Killing of Satomi Mitarai

On June 1, 2004, at Okubo Elementary School in Sasebo, Nagasaki Prefecture, Japan, 12-year-old Satomi Mitarai was killed by an 11-year-old female classmate, referred to publicly at the time as "Girl A" due to Japanese laws prohibiting identification of juvenile offenders. According to Wikipedia's account of the case, during a school break between 12:15 and 12:35 PM, the classmate called Mitarai to an empty classroom approximately 50 meters from their regular classroom, reportedly telling her "Your attitude is insolent" and "Come here for a moment." Once inside, the classmate closed the curtains, had Mitarai sit in a chair, covered her eyes, and slit her throat and arms with a box cutter from behind. Mitarai attempted to resist but was slashed repeatedly.

The perpetrator returned to her own classroom with blood on her clothing. A teacher, checking her for wounds, found none and pressed her for an explanation; she reportedly said "It's not my blood. It's not me." The teacher then discovered Mitarai's body. After being taken into custody, the classmate reportedly confessed to police, repeatedly apologizing. She told investigators that she and Mitarai had once been close friends, but their relationship deteriorated after exchanges on an online chatroom site, during which she said Mitarai had commented on her weight and called her a "goody-goody."

On September 15, 2004, a Japanese Family Court ordered the girl institutionalized in a reformatory facility in Tochigi Prefecture, citing the severity of the crime despite her young age. Her original two-year commitment was extended by two years in September 2006 following a psychological evaluation. On May 29, 2008, authorities announced no further sentence would be sought. She was later reported to have been diagnosed with Asperger syndrome following the killing.

The case prompted a national debate in Japan about whether the age of criminal responsibility, which had been lowered from 16 to 14 in 2000 following the 1997 Kobe child murders, should be lowered further. Public commentary intensified because the perpetrator had reportedly been considered a normal, well-adjusted child prior to the incident. Two members of the Japanese Diet faced public criticism for remarks made about the case. Online, the perpetrator became the subject of an internet meme after a class photograph purportedly showing her in a University of Nevada, Reno sweatshirt led to the nickname "Nevada-tan" circulating on Japanese web forums. The case was also cited, controversially, in support of a discredited theory linking video game use to violent behavior. In 2019, an audio drama referencing the case and titled after the online nickname was released on Audible.