Masahiro Kanagawa was born on October 13, 1983, in Japan. Publicly available details about his early childhood, family environment, and education remain limited. However, reports indicate that Kanagawa led a relatively quiet and withdrawn lifestyle prior to his crimes. He was known to enjoy playing video games, particularly action and combat titles like Ninja Gaiden: Dragon Sword. Some media speculation after his arrest linked his obsession with these games to his violent actions, though no psychological diagnosis was officially disclosed.

Masahiro Kanagawa’s violent rampage began just days before his most well-known act. On March 19, 2008, he murdered a 72-year-old man in a seemingly unprovoked attack. This crime went unsolved for several days until he reemerged with deadly force.

On March 23, 2008, in the city of Tsuchiura, Ibaraki Prefecture, Kanagawa launched a random stabbing spree in a busy area near Arakawaoki Station. Armed with two knives, he targeted commuters walking along a short connecting hallway at the station. During the spree, he fatally stabbed a 27-year-old man, who later died while being rushed to the hospital, and seriously wounded seven others. The victims were not known to him, and the attack appeared completely indiscriminate.

After the assault, Kanagawa was quickly subdued and arrested by police at the scene. During interrogation, he stated plainly that he "just wanted to kill anyone." His comments shocked the nation and fueled debates about the mental health system, media violence, and capital punishment in Japan. Reports suggested that he had been hiding in Akihabara prior to the attack and was possibly influenced by violent video games, though such claims remained speculative.

Kanagawa was later charged not only for the Tsuchiura spree but also for the earlier murder committed four days prior. On December 18, 2009, the Mito District Court sentenced him to death by hanging. He did not contest the ruling and reportedly sought execution as a form of self-imposed punishment.

Masahiro Kanagawa was executed by hanging on February 21, 2013, just over four years after his conviction.