Tsutomu Miyazaki was born on August 21, 1962, in Itsukaichi, Tokyo. He came from a wealthy family that owned a regional newspaper company. His family was well-known in their community, and both his grandfather and great-grandfather had served on the town council. Tsutomu was born premature and had a rare birth defect that left his hand joints fused together. This condition prevented him from bending his wrists upwards.

Because his parents were often busy with work, Miyazaki was primarily raised by his grandfather and a man with an intellectual disability, who the family had hired as a nanny. His early life was marked by isolation, especially when he entered elementary school. Due to his deformity, he was ostracized by his classmates, leading him to become withdrawn and keep to himself.

Later, he attended Meidai Nakano High School, which was a prestigious school connected to Meiji University. In the beginning, he was a star student. However, his grades began to decline, and he ended up ranked 40 out of 56 in his class. Because of this, he did not gain automatic admission to Meiji University as he had hoped. Instead of pursuing his original plan to become an English teacher, he opted to attend a local junior college, where he studied to become a photography technician.

In the mid-1980s, Tsutomu Miyazaki moved back into his parents' house in Itsukaichi. He shared a room with his older sister. His family was influential, but he showed no interest in taking over their business. After his arrest, he stated that what he really wanted was to be listened to about his problems. He felt that his parents were more concerned about material things than emotional connection, and believed they would have ignored his feelings. At this time, he also began to contemplate suicide, feeling isolated and misunderstood.

Miyazaki was particularly close to his grandfather, who had passed away in May 1988. This loss deepened his depression and sense of isolation. In a strange act of mourning, he attempted to "retain something" from his grandfather by eating part of his ashes. Shortly after, one of his sisters caught him acting inappropriately and told him to leave her alone. This confrontation escalated, leading to an attack on her. When his mother found out about this incident, she demanded he spend more time working and less time watching videos. This demand led to another violent encounter with her.

Between August 1988 and June 1989, Tsutomu Miyazaki committed a series of gruesome murders in Tokyo and Saitama Prefecture. He killed four young girls aged between four and seven years. His crimes became widely known as the "Little Girl Murders."

On August 22, 1988, Miyazaki kidnapped a four-year-old girl named Mari Konno. He lured her into his car and took her to a secluded spot. After the murder, he disposed of her body in the hills near his house. He later returned to remove her hands and feet, which he kept as trophies. He burned her remains and sent a box of her ashes, teeth, and a postcard to her family.

Two months later, on October 3, he abducted seven-year-old Masami Yoshizawa from a rural area. Like with Konno, he took her to the same location and killed her. He took away her clothes and discarded them after the murder.

On December 12, 1988, Miyazaki targeted four-year-old Erika Namba. He forced her into his car while she was walking home. He killed her in a parking lot and hid her body in his trunk. Three days later, her body was found nearby.

The last of Miyazaki's victims was five-year-old Ayako Nomoto, who he lured into taking pictures on June 6, 1989. After killing her, he kept her body in his apartment for two days. Eventually, he dismembered her and hid her remains in several locations, including a cemetery and his closet.

Miyazaki's crimes shocked the community, and he was arrested on July 23, 1989, after being caught while attempting to photograph another girl. The investigation led to the discovery of videotapes and photos of his victims in his home. After a long trial, he was convicted of multiple murders and sentenced to death. He was executed on June 17, 2008.