Sadako’s initial origin story is related in the novel and the first film. She lives on Oshima island with her mother Shizuko, a deeply disturbed woman who also has psychic powers. Shizuko gives birth to Sadako in a cave, where she hopes her child would be carried away by the waves. When she returns the next day, however, Sadako is still there, and so Shizuko keeps her.
As a child, Sadako is painfully shy and rarely socializes with other children. One day, a cousin, Takashi, decides to profit from Shizuko’s powers and contacts Dr. Heihachiro Ikuma, a scientist fascinated by psychic powers. Heihachiro and Shizuko eventually form a romantic relationship, and they marry. This union, however, becomes strained when, during a public demonstration of her powers, Shizuko is mocked and insulted by reporters who accuse her of being a fake. Sadako, in defense of her mother, launches a psychic attack which kills the reporter who started the chaos. Sadako suddenly splits into two people; one kind-hearted and timid, the other violent and psychotic. The good Sadako is allowed to live on while the other is kept in seclusion and forced to take growth-inhibiting drugs. Shizuko eventually breaks under the strain and throws herself into Mount Mihara.
Sadako’s full origin is revealed in Ring 0. At the age of 19, she joins an acting troupe in Tokyo Osaka Kōchi, and is immediately looked upon with suspicion when a number of actors die under mysterious circumstances. Unknown to Sadako, her twin is the actual culprit, using her as a conduit. Sadako enters a relationship with a sound editor named Toyama, the only person who shows her any acceptance. A set of calamitous circumstances result in Sadako being beaten to death by the acting troupe and taken to Dr. Ikuma’s home, where they intend to finish off the evil Sadako. The plan fails disastrously, resulting in the two Sadakos merging into a single entity of pure destruction. Sadako kills the entire troupe, including Toyama. Dr. Ikuma beats her over the head with an axe and throws her down a well, where she survives by sheer will for over 33 years.
During her entrapment, a summer resort is built over the well. Using her powers, Sadako projects a series of images from her past into a blank videotape which, when watched, would kill the viewer after seven days.
