Mamoru Takuma was born on November 23, 1963, in Itami, Hyōgo Prefecture, Japan. He was a troubled child who showed unusual and anti-social behavior from an early age. At just three years old, he rode his tricycle into the middle of a busy highway, causing traffic jams. He also harmed small animals, wrapping them in newspaper and setting them on fire.

As he grew older, Takuma experienced bullying in school. He was both a victim and a bully. He often felt envious of those who were highly educated and had higher incomes. His home life was difficult. His father physically abused him and neglected him, which led Takuma to have violent thoughts about his father.

In February 1979, Takuma started high school in Amagasaki. However, he dropped out in March 1981. After a short time working part-time at a gas station, he joined the Japan Air Self Defense Force at 18. He was discharged in January 1983 because he had a relationship with a teenage runaway. This event worsened his relationship with his parents. His father often beat him, sometimes with stones, and Takuma threatened to join the yakuza to get back at them.

In 1984, Takuma and his mother moved out of the family house and lived in an apartment. They left his oldest brother and father behind. They lived together for about a year and a half until his father returned to try to bring the family back together. In February 1999, Takuma's brother died by suicide while facing bankruptcy. This tragedy affected the family deeply. Takuma's father struggled with alcoholism afterward, and Takuma expressed a wish that his father should have also taken his life.

Takuma's mother had issues with mental illness throughout her life. She passed away in late 2016, and his father died in April 2020. The house where Takuma grew up in Itami was demolished in September 2020, leaving the site empty.

On 21 November 1984, Mamoru Takuma committed a rape while collecting rent for a condominium management company. Following the incident, he feared the victim might report him to the police. On 12 December, he visited a psychiatrist with his mother, where he mentioned experiencing hallucinations and other mental health issues. Initially diagnosed with anxiety, the hospital later identified him as having schizophrenia.

Takuma was admitted to a closed psychiatric ward but became unhappy with the care he received. On 4 January 1985, he attempted suicide by jumping from the fifth floor of the hospital, resulting in fractures to his jaw and face. After his release, he expressed a desire for revenge against the world. He was convicted of rape in November 1986 and served three years in prison.

After his release in March 1989, Takuma worked as a driver but was involved in two fatal car accidents. The first caused multiple fatalities, but he lied about it and faced no charges. The second incident also resulted in a death, after which he fled the scene. In September 1993, he was arrested again for rape.

He later worked various jobs but was often fired due to violent outbursts and mental health issues. On 3 March 1999, he sent four people to the hospital by dissolving a tranquilizer in their tea.

On 8 June 2001, while facing court for a previous assault, Takuma attacked Ikeda Elementary School with a kitchen knife. In this attack, he killed eight students, including seven girls and one boy, and injured fifteen others. When arrested, he was confused and made contradictory statements about where he had been.

During his time in custody, he took medications in excessive quantities but claimed they affected his mental state. Takuma expressed a desire to be sentenced to death. His trial began soon after, where his lawyers claimed he was temporarily insane. However, a psychiatrist later diagnosed him with a paranoid personality disorder.

On 28 August 2003, he was convicted of multiple counts of murder and sentenced to death. He showed no remorse during the trial and made provocative statements. Takuma was executed on 14 September 2004, just over a year after his conviction.