Nami Tsuchiya, Miyuki Ono, a late-night TV show host, invites her viewers to send in home movies, a prompt that leads to a disturbing discovery. A snuff film shot at a disused military base surfaces, featuring a woman who bears an uncanny resemblance to Nami. The footage ends with a photograph of her own face, a detail that unsettles her and sparks questions about who could have produced it and why.
The station, unsure if the clip is real or staged, forbids airing the footage but sees potential for a sensational story. They decide to let Nami relocate her small production crew—Rie, Mako, Rei, and Kondo—to the deserted site to investigate the origins of the film. The goal is simple in theory: locate the culprit, or at least uncover the truth behind the disturbing footage, before the show’s finances totally collapse from a lack of audience interest.
Upon arrival, the base feels empty and ancient, almost alive with the memory of past activity. The crew splits up to cover more ground, hoping to stumble upon clues that tie the film to a producer, a location, or a motive. Hidden dangers lurk close by, however, and the killer behind the snuff film begins to shadow their movements, moving with a patient, malignant certainty.
Nami encounters a mysterious man, Daisuke Muraki, Yūji Honma, who appears to know more about the base’s darker history and warns her to leave. He hints at a connection to someone he’s searching for and vanishes before he can reveal more, leaving Nami with a growing sense of unease.
Back with Rei Sugiura, Hitomi Kobayashi and Kondo, the pair’s relationship adds a charged undercurrent to their exploration. In a forgotten workshop, Rei and Kondo share a tense private moment, but tragedy soon follows when Rei cleans her clothes and discovers the body of the snuff-film victim instead of her partner. The killer strikes quickly, impaling Rei with several metal poles and ending her life.
The mood intensifies as Kondo reunites with Nami and the others at the work van. Nami admits to a personal motivation behind her investigation, something that goes beyond journalistic curiosity. Mako, having traced the building where the film was created, leads the group inside. They confront the horrifying reality of Rei’s corpse rigged to frighten them, and Rie, overwhelmed by fear, escapes as the ceiling collapses, trapping the remaining crew inside.
Rie reaches the van, but danger follows: she is intercepted by the snuff-film victim’s prisoner, a man kept alive only to serve the killer’s twisted needs. He reveals that the killer promised freedom if he killed trespassers, then abuses Rie before meeting his own end. The revelation makes clear that the killer is driven by a monstrous thrill—two entities in one, neither fully human.
As the survivors scramble to escape, they become separated. Nami and Kondo plummet through a floor hole, while Mako is assaulted by the killer and knocked unconscious. Nami comes to on a rooftop and discovers Kondo’s headless body nearby. Daisuke reappears, having returned to the scene to confront the threat, and explains that he once lived on this base with his brother. He ventures off to face the killer, but a spear strikes him, and he does not return.
Nami pushes forward, seeking answers and rescue. She follows a television broadcast showing Mako pleading for help, racing to reach her fallen colleague. A trap in the room where Mako is held claims her life just as Nami tries to intervene. The killer then escalates, using fireworks and arrows to press the attack, until Daisuke appears again, providing cover fire and guiding Nami toward safety through an underground passage. He gives her a gun and cautions that the culprit is “a kid,” vowing to finish the job himself.
Returning to the safe van, Nami confronts the grim sight of the killer dragging away the bodies of Rie and the prisoner. She resolves to pursue justice, determined to see the killer brought to account. The final confrontation unfolds in the killer’s hideout, where Nami discovers a bedroom filled with disturbing artifacts: photographs of the killer as a child with his mother, rows of televisions streaming footage of her show, and voice recordings of the killer’s mother.
The truth behind the killings emerges: the two “in one” killers are Daisuke and his twin brother Hideki, a mutant infant living inside Daisuke’s chest with psychic abilities, capable of teleportation and fire-breathing. Weary of the killing, Daisuke allows Nami to shoot him, but Hideki erupts from his chest and attacks once more. Daisuke traps Hideki back inside his chest and sets himself on fire, dying in a charred eruption that nearly suffocates Nami before she fights free with shards of glass.
In the hospital, a detective tells Nami that the police found nothing to confirm Hideki’s existence, and the report is amended as if she had imagined the whole thing. Nami’s broadcast pays tribute to her colleagues, earning widespread acclaim. Yet a chilling postscript follows: a parcel arrives containing the lighter used by Daisuke, and Nami senses a new threat. The marks on her neck begin to ache, and she realizes that Hideki may have infiltrated her body. In a final, terrifying moment, Hideki forcibly births from Nami’s stomach, addressing her as “Mommy.”
