Plot

The vengeful spirits of the Ring and Grudge series face off.

A social worker visits the residence of an elderly woman, only to find her strangled by an electric cord. A nearby video player suddenly turns on and plays the cursed videotape. As she watches, Sadako Yamamura appears and kills the social worker.

The video player is sold at a shop and bought by university students Yuri Kurahashi and Natsumi Ueno. When they find the cursed videotape inside, they play it. The footage has been upgraded, displaying a decrepit building instead of the usual well, and the curse deadline has been reduced to two days. Yuri gets distracted by her phone, leaving Natsumi to watch the tape in its entirety by herself. Afterward, they receive a disturbing phone call as Sadako manifests in the room behind Yuri, startling Natsumi.

A worker at the shop who had watched the cursed tape leaps to her death. The girls go to return the video player and learn about the deaths related to the tape. Desperate, they go to their professor, an author on urban legends, Shin'ichi Morishige. Obsessed with the idea of meeting Sadako, Morishige eagerly watches the tape, although the girls are less than thrilled, as Natsumi only has one day to live. After he receives a phone call, Morishige takes the girls to an exorcist, but Sadako possesses Natsumi and forces the assistants to kill themselves before the exorcist begins to boil from the inside and kills Morishige for interfering. With her dying breath, the exorcist tells the girls that a man with psychic powers, Keizo Tokiwa, will help them.

When a despondent Natsumi blames Yuri for her situation, Yuri watches the tape, hoping that this will pass the curse on to her and Natsumi will be spared. Keizo arrives, accompanied by a blind psychic girl, Tamao, who tells Yuri that she has unnecessarily cursed herself. The only way to expunge the curse is to pit Sadako against another vengeful spirit so both destroy each other. As Yuri hears that Natsumi has uploaded the cursed tape onto the Internet, Natsumi tries to commit suicide to escape her imminent death. Whilst Yuri rushes to save Natsumi, Sadako appears before Natsumi and kills her via hanging. Keizo and Tamao target Kayako Saeki to be the rival spirit.

Meanwhile, high school student Suzuka Takagi starts having dreams of the haunted Saeki house after moving in nearby with her family. She runs into Keizo and Tamao, who states that the house beckons to Suzuka, he warns her not to enter or she will be killed. After Suzuka leaves, a group of bullies arrive and force a schoolboy to enter the Saeki house. However, Kayako and Toshio violently drag all of them to their demise, including the schoolboy and the group leader who gets killed by having his head snapped off by Toshio.

That night, Suzuka thinks she sees a schoolboy inside the Saeki house and goes inside. She sees Toshio and her screams prompt her parents to rush in, only to be killed by Toshio and Kayako. Keizo saves Suzuka, but she is already cursed. Yuri and Suzuka agree to team up for Keizo's plan, where they enter the Saeki house so that Suzuka can watch the cursed videotape inside and Yuri can see Kayako, thus becoming afflicted with both curses. Keizo hopes this will make Sadako and Kayako fight over the girls and obliterate each other in the process.

As the plan unfolds, Toshio appears, but Sadako drags him inside the TV as he screams. Sadako crawls out of the TV whilst Kayako crawls downstairs, they brutally confront each other, but the battle ends in a stalemate. Keizo reveals his last resort: one of the girls has to lure both ghosts into a well outside of the house so they can be sealed inside. Yuri chooses to sacrifice herself, jumping into the well as Sadako and Kayako begin to rush toward her, resulting in a massive collision that bisects Keizo and turns both ghosts into a giant mass of hair, flesh, and eyes. The giant mass falls into the well, presumably crushing Yuri to death. Suzuka seals the well and imprisons the ghosts.

This last resort does not work either, and instead backfires terribly: both Sadako and Kayako's curses combine and become a single entity: Sadakaya. Now possessing Yuri's body with the appearance of Sadako, a combined movement of both spirits and the sound of Kayako's death rattle. Suzuka screams in horror, and Tamao's psychic powers are overwhelmed. Toshio reappears behind them, and the girls' fates are left unknown.

In a post-credits scene, the modified version of the cursed videotape is shown. Sadakaya menacingly contorts her body, imitating the movements of both Sadako and Kayako. She then teleports to the screen, emitting a death rattle.