The character referred to as the Child Murderer from The Ring is known as Sadako Yamamura. It is important to clarify that The Ring is not an anime but a Japanese horror franchise originally based on a novel series by Koji Suzuki, which has been adapted into numerous live-action films, television series, and manga. Sadako is the central antagonist and a powerful onryō, a vengeful spirit from Japanese folklore.

Sadako was born in 1947 on Oshima Island as the daughter of Shizuko Yamamura, a renowned psychic, and was raised by her stepfather or presumed father, Professor Heihachiro Ikuma, after her mother’s death. As a child, Sadako possessed immense psychic powers. When journalists publicly denounced her mother as a fraud during a demonstration, a young Sadako used her abilities to kill one of them, an act that foreshadowed her later nature. Following her mother’s suicide, Sadako’s uncontrollable powers and an incident where she split into two beings—one benign and one malevolent—led Ikuma to inject her with poison and throw her down a deep well, where she survived for thirty years on sheer hatred before finally dying.

In life, Sadako was an isolated and socially awkward individual who struggled to fit in. She briefly pursued a career as a theater actor but was unable to maintain normal relationships due to her unsettling aura and powers. A defining aspect of her character in the original novels is that she had testicular feminization syndrome, a condition that made her appear female but unable to reproduce, a biological fact that deeply influenced her motivations. Her personality is defined by the immense trauma, betrayal, and loneliness she suffered, which festered into an all-consuming hatred for humanity. She is not driven by malice in a personal sense but by a mechanical and absolute will to spread the curse of her own suffering, forcing others to experience a fraction of the terror and isolation she felt in the well.

Sadako’s role in the story is that of a tragic monster whose curse drives the plot. After her death, she created a cursed videotape using her psychic powers. Anyone who watches this tape dies exactly seven days later, often of a heart attack induced by sheer terror, unless they copy the tape and show it to another person, perpetuating the cycle. Her goal is not simply to kill but to reproduce and survive. The curse is, in effect, a virus—the Ring Virus—a mutation of the smallpox virus combined with her own DNA. This virus ensures her resurrection and proliferation, as it can impregnate victims with clones of herself. The key relationships in her existence are primarily antagonistic. Her father, Ikuma, was her murderer, whose act of betrayal is the source of her curse. In the prequel film Ring 0: Birthday, she forms a tragic romantic connection with a sound manager named Toyama, who accepts her powers, but this relationship ends in catastrophe due to the interference of others. Her entire existence as a spirit is defined by her relationship with those who watch her tape; they are her victims, but also the necessary hosts for her continued existence.

Throughout the various continuities, Sadako undergoes significant development, often depending on the adaptation. The most notable evolution occurs in the novel Spiral, where her plan succeeds. The Ring Virus leads to her physical resurrection as a being who can now reproduce, effectively allowing her to supplant humanity. In other timelines, such as the American remakes where she is renamed Samara Morgan, her background is altered to emphasize her tragic childhood as an unwanted child with uncontrollable powers, shifting the focus more toward her desperate need for a mother than biological replication. In the manga Sadako-san and Sadako-chan, her character is subverted entirely when she befriends a young girl who is not afraid of her, leading Sadako to seek a form of peace.

Sadako possesses a vast array of notable abilities, the most famous of which is nensha, the psychic ability to burn images from her mind onto physical media like film or videotape. As a ghost, she can manipulate technology, particularly televisions and VCRs, using them as portals to emerge from and interact with the physical world. She has demonstrated telekinesis, the power to move objects with her mind, and can induce heart attacks or death simply by staring at a victim. Her physical form is that of a classic yūrei: a woman in a white burial dress with long, black hair covering her face. She can crawl out of wells and other surfaces, contorting her body in an unnatural, jerking fashion that defies human anatomy. Her curse also has the property of corrupting her victims, turning them into vengeful spirits who serve to propagate her curse further.