A mysterious white-clad man throws a long-haired woman into a well that is already full of similar women. This is the work of Seiji Kashiwada, a disturbed online artist who seeks to resurrect the legendary ghost Sadako Yamamura as an act of revenge against humanity. He began by kidnapping women and throwing them into the well, but when that failed to produce the desired result, he created a cursed video. In the video, Kashiwada films himself being killed by a ghost and then uploads it to the internet, causing anyone who watches the footage to die as well. The video serves as a tool to find a perfect human host for Sadako.

The story shifts to Akane Ayukawa, a high school teacher with latent telekinetic powers. Years earlier, she used these abilities to stop a maniac from attacking her school, an act that branded her a freak rather than a hero. Only Takanori Ando, a boy who appreciated her power, remained close to her, and he has since become her boyfriend. In the present day, Akane hears rumors from her students about a suicide video circulating online that drives its viewers to kill themselves. She dismisses the story until one of her female students, Noriko Morisaki, watches the footage and dies.

Investigating the death, Detective Koiso and his partner discover a pattern of similar suicides. Akane also looks into the matter with Takanori, a video designer, and learns that the video is connected to Kashiwada. When Akane saves another student, Risa, from being attacked by the ghost that emerges from the video, the spirit declares that Akane is "the one". The curse begins targeting Akane directly, forcing her and Takanori to flee. The ghost, able to emerge from any screen, pursues them through a large LCD display truck on the street and ultimately captures Takanori, trapping his essence inside a mobile phone.

Akane teams up with Detective Koiso, who has discovered that Kashiwada’s apartment was a stage set, its walls covered in white butterflies hiding the madman’s notes and history. Kashiwada had been tormenting Akane specifically, believing her unique powers make her the ideal vessel for Sadako. Koiso and Akane travel to the old Yamamura property, now a decrepit building beside a mall. At the well, they are attacked by the mutated, imperfect versions of Sadako created from Kashiwada's earlier victims, and Koiso is killed.

Akane makes her way to a room where she is confronted by a legion of the imperfect Sadakos. Her fear triggers her telekinetic powers, destroying the creatures. She is then transported to the roof where the real Sadako is waiting with the captive Takanori. Sadako reveals that she and Akane are the same, but Akane rejects this, stating that Sadako uses her power to destroy while she uses hers to help others. To save Takanori, who has a knife at his throat, Akane agrees to become Sadako's host. The ghost engulfs her in a torrent of black hair, but Takanori, now freed, destroys the mobile phone trapping him. Akane falls to the floor below, covered in the ghost's hair but alive and human. A mid-credits scene reveals Kashiwada may have survived, as the opening of his cursed video begins to play again with a slight alteration to his introduction.