Sachiko Eto was born on August 21, 1947, in Sukagawa, Fukushima, in Occupied Japan. She grew up in a region that was recovering from the effects of World War II. Information about her childhood is limited, but she graduated from high school and later married her sweetheart. They lived an ordinary life along the Abukuma River. Sachiko worked in cosmetics sales, while her husband was a paint craftsman.

In the early 1990s, Sachiko's life began to change dramatically. Her husband injured his back and stopped working. This led to problems as he turned to drinking and gambling, causing them to fall deeper into debt. Eventually, they sold their home and moved to Gifu Prefecture. There, they joined a religious group linked to Shinto beliefs that focused on spiritual healing. However, their unauthorized use of the group's name got them expelled.

After her husband disappeared in 1992, Sachiko found herself alone with their daughter. She moved to Sukagawa in Fukushima and started performing spiritual healings. Over time, she began claiming that she had psychic abilities and proclaimed herself a god. As she attracted more followers, her claims and rituals became more extreme.

Sachiko's community grew, and she often held gatherings that involved chanting and drumming. Neighbors complained about the noise and the numerous cars lining the street, but they were afraid to confront her. Sachiko threatened a neighbor who complained, saying she could hypnotize and disable her.

As her followers increased, so did the intensity of her rituals. Sachiko claimed she could drive out demons and began using violence during these ceremonies. She often involved her daughter in these acts.

From December 1994 to June 1995, Sachiko Eto and her followers were involved in a series of murders in Sukagawa City, Japan. Eto claimed to be a healer and performed rituals to drive out what she called "ugly devils." Her followers included her daughter Yuko, Hiroshi Nemoto, and Mitsuo Sekine. Together, they attacked and killed several cult members during these bizarre ceremonies.

On July 5, 1995, police searched Eto's house after a female cult member was hospitalized due to serious injuries. Inside, authorities discovered six decomposing bodies hidden within the house. The victims were identified as individuals linked to Eto's cult, including the wives and children of her followers. Following the discovery, Eto and her three accomplices were arrested. The surviving female member was also charged for her role in the violence.

During the trial, Eto insisted that none of the deaths were intentional. She maintained that her actions were part of a religious service aimed at exorcising demons. Despite her claims of mental illness, the court found her guilty of murder and sentenced her to death. Her daughter and other followers received life sentences and lengthy prison terms.

Eto's death sentence was upheld through various appeals in the following years. On September 17, 2012, she was executed by hanging in Miyagi Prison, marking her as the first woman to be executed in Japan in 15 years.