Nevada-tan is the name used to describe an 11-year-old Japanese schoolgirl who murdered her classmate Mitarai Satomi. The murder occurred on June 1, 2004 at an elementary school in Sasebo, Japan and involved the slitting of Mitarai's throat and arms with a boxcutter.
The incident has come to be known as the "Sasebo Slashing". The killer, officially referred to as "Girl A" (real name undisclosed as per Japanese legal procedures), has since become an internet meme character dubbed "Nevada-tan", after the University of Nevada hooded sweater she was wearing at the time.
This event was the inspiration behind the Vocaloid song Shoujo A.
