In Japan, a school’s movie club was shut down after one member vanished and another was hospitalized from a nervous breakdown. Seven years later, two students, Maki Yoko Mitsuya and Ai Chisato Morishita, restart the club with the goal of making a horror film based on the events that ended the club’s life. Three other girls (Natsuki Yuko Kurosawa, Yayoi Keiko Saitō, and Yuka Yukari Fukui) join the project, and they, Maki and Ai, are taken to a secluded lodge called the Yuai House by Maki’s sister Yoko, a teacher and former club member, who has brought along the awkward Takako Nozomi Ando.
Once everyone settles in, Maki and Ai show the others an old 8mm tape they found while cleaning the club room at the school. The tape, titled Gurozuka, is set at the lodge and depicts someone wearing a Noh mask killing their co-star with a meat cleaver. The students debate whether the murder shown on the tape was real, and the next day the car fails to start, and all the food, cell phones, and wallets vanish, along with the Noh mask and cleaver that were to be used in the film project.
When night falls, Natsuki disappears, and Takako and Yuka are non-fatally poisoned, prompting Yoko to leave in search of help. In the morning, Ai reviews footage shot by Natsuki, which shows her being assaulted by someone wearing the Noh mask. Ai runs outside and finds Maki, who claims to have seen the masked woman just moments ago. The two then discover the missing food dumped in the woods, along with the Noh mask and the now-bloodied cleaver. The girls return to the house, and discover Takako and Yayoi are gone, so they search for them along with a recovered Yuka, soon stumbling onto the bodies of Natsuki and Yayoi. The trio returns to the lodge (where Takako has been hiding) and decides to hold out until morning. A bloodied Yoko appears banging on the door, begging for help, moments before the Noh-masked figure breaks in.
Ai is chased outside by the killer, and finds Yuka’s corpse, and a delusional and dying Takako. The murderer catches Ai and pulls off the Deigan mask to reveal she is Maki. Maki explains that after finding the Gurozuka tape she became obsessed with it, and that it made her want to kill. Ai escapes, and Maki gives chase again, after stabbing Yoko in the head. When Maki finds Ai, she professes her love for her, and then claims she is going to cannibalize her body to become her. Before Maki can make the killing blow, Ai stabs her in the chest with a nail the two had earlier found stuck in a tree.
Ai wakes up at the Yuai House, and joins Yoko (whom she had found alive, and saved) in watching Gurozuka, which Yoko muses seems to drive people insane. When Ai tries to destroy the tape, Yoko grabs her, and repeats Maki’s line:
> You’re such a good girl. I want to be you, Ai.
