Junko Ogata was born on February 25, 1962, in Kurume, Fukuoka Prefecture, Japan. She grew up in a wealthy family. As a child, she lived a comfortable life and was considered a gentle person. Junko went to school where she met Futoshi Matsunaga, but they were not close friends, and he transferred to another school before they became acquainted.

After finishing her education, Junko got a job at a preschool. She enjoyed her work and seemed to have a promising future. In 1982, she began dating Matsunaga. This relationship marked a significant change in her life. Before meeting him, she had remained a virgin. However, Matsunaga was often insecure and suspected her of being involved with other men.

During their relationship, Junko and Matsunaga had two sons together. Unfortunately, Matsunaga was abusive towards her. He accused Junko's mother of trying to seduce him, which led to more violence against Junko. Over time, Junko began to suspect that Matsunaga may have harmed her mother in other ways.

Junko Ogata was involved in a series of murders alongside Futoshi Matsunaga between 1996 and 1998. They killed at least seven people, including Ogata’s family members, such as her sister, her sister's husband, and her niece and nephew. They also murdered a man named Kumio Toraya. Their crimes shocked the community in Japan.

On March 2002, Ogata was arrested for her involvement in these murders. The case received significant attention, and over time, a Japanese writer named Masayoshi Toyoda wrote a book questioning the details of the trial. He wanted to support Ogata and create doubt about her guilt. He first attempted to meet her on September 27, 2005. At that time, she was still labeled a murderer, but eventually, he was allowed to see her.

On September 28, 2005, a district court in Fukuoka sentenced Ogata to death. She filed an appeal on October 11 of the same year. The court considered six murders, while the death of Ogata's father was classified as manslaughter. On September 26, 2007, the high court in Fukuoka changed her sentence to life in prison, rejecting the death penalty. Prosecutors appealed this decision to the Supreme Court, which confirmed her life sentence.