Toi Mutsuo was a young Japanese man who carried out a mass killing in May 1938 in a village near Okayama, taking the lives of thirty people before killing himself. The attack, carried out in the early hours of May 21, 1938, was one of the deadliest single-perpetrator massacres in Japan up to that time.

Key Facts

• Toi Mutsuo killed 30 people in a single night on May 21, 1938.
• The massacre was, at the time, one of the worst committed by an individual in the country’s history.
• Mutsuo died by suicide at the scene, shooting himself after the attacks.
• He used multiple weapons during the rampage, including a shotgun, an axe, and a katana.
• His grandmother was killed first; reports indicate she was decapitated with an axe.
• Before moving through the village, he cut the electrical supply and strapped torches to his head to illuminate the night.
• Notes attributed to Mutsuo referenced depression and the social rejection he experienced because of tuberculosis.
• He was 21 years old at the time of the killings and had been suffering from tuberculosis, then considered incurable.
• The killings took place in the small community of Kaio, on the outskirts of Okayama.
• Mutsuo had been raised by his grandmother after his parents died when he was young.

Crimes and Victims

The violence began in the predawn hours of May 21, 1938, when Mutsuo entered homes in the village and attacked residents found inside. He moved systematically from house to house, using a shotgun for many of the killings and resorting to an axe and a katana in other instances.

Victims included men, women and children from the small community of Kaio. Contemporary reports list thirty fatalities in total, making the incident a mass-casualty event that shocked the local area.

Capture and Trial

There was no arrest or criminal trial in this case because Mutsuo died at the scene. After completing the attacks, he shot himself in the chest with the shotgun he had used during the spree.

As a result, legal proceedings against him did not take place and no formal sentencing was issued. Investigations by authorities focused on documenting the sequence of events and identifying the victims rather than prosecuting the perpetrator.

Psychology and Motives

Accounts from the time indicate Mutsuo suffered from tuberculosis and severe depression, and his writings reportedly referenced feelings of rejection connected to his illness. These notes have been cited as suggesting personal despair and social isolation were factors in his decision to carry out the attacks.

There is limited contemporaneous psychological evaluation recorded, so definitive conclusions about his mental state remain speculative. Histories of the case emphasize the interaction of chronic illness, social exclusion and acute distress as likely contributors to his actions.

Background / Early Life

Toi Mutsuo was born into a family that lost both parents at a young age, and he was subsequently raised by his grandmother. He lived in Kaio, a small rural village near Okayama, where social ties and reputation played important roles in daily life.

By age 21 he had developed tuberculosis, an illness that at the time carried not only serious health consequences but also social stigma. Sources note that his illness affected his social relationships and employment prospects, and that rejection by local women preceded the outbreak of violence.

Legacy and Media Coverage

The scale of the killings made the event a significant news story in Japan in 1938, generating attention in regional and national press. Reporting emphasized both the shock of the community losses and the apparent motives linked to illness and social rejection.

Over time the incident has been referenced in discussions of mass violence in prewar Japan and in studies of how illness and isolation can factor into violent acts. The case remains a noted example in historical surveys of individual-perpetrated mass killings in the country.