Reijiro Hieda, Kenji Sawada, is a young and energetic archaeologist whose enthusiasm for the supernatural is dismissed by his peers. A letter from his brother-in-law, Takashi Yabe, Naoto Takenaka, a junior high school teacher, recounts the discovery of an ancient tomb built to seal a yōkai. When Yabe and his student Reiko Tsukishima, Megumi Ueno, investigate the burial mound, they disappear, leaving questions hanging in the air.
Upon arriving in town to probe the mystery, Hieda meets Masao Yabe, Masaki Kudou, Yabe’s son, who has already been haunted by chilling phenomena. Masao recalls a troubling scene at the schoolhouse where a returned Reiko supposedly seduces his classmate Kono, and he begins to suffer from a string of uncanny afflictions—backache that heats up, rising smoke, and the sight of small, blackened faces of the dead. Together, Masao and Hieda follow a trail of clues through the schoolhouse, discovering Kono along with his friends Aoi and Katagiri, who are later found murdered in a brutal, almost ritual manner with a switchblade.
At first, the pair suspects the janitor, Watanabe, a quiet man who had previously tried to keep people away from the schoolhouse. But the evidence soon points to something far more sinister: the disembodied singing head of Reiko herself, a haunting specter that seems tethered to the tomb’s curse. As Hieda delves into Yabe’s notebook, he learns that the tomb holds Hiruko, a yōkai whose escape could unleash calamity. With this knowledge, Hieda resolves to learn the ancient spells required to both enter the burial chamber and seal it again, lest the town be swallowed by the otherworldly threat.
Watanabe, who had earlier severed the power lines to the schoolhouse, attacks the pair in a bid to halt their investigation. Masao, showing unexpected resourcefulness, wrests a gun from the assailant during the struggle. They retreat to the schoolhouse, where Reiko, now with spider-like legs, closes in on Masao and continues to menace them. A tense escape follows, but Reiko reappears later with insect-like wings, and the four clash once more. Reiko’s assault is briefly repelled by a spray of bug repellent, allowing the investigators to pull back and regroup.
In a crucial flash of meaning, Watanabe reveals a deeper past: he once knew Tatsuhiko Yabe, Masao’s grandfather, who bore the scars of dead men’s heads on his back and who, long ago, sealed the gate to prevent tragedy from repeating itself. He confesses that he was sworn to guard the schoolhouse after Tatsuhiko’s death, and he hints that the missing crown—the sacred Yabe family treasure needed to seal Hiruko—may still lie within the sealed chamber. The revelation shakes Hieda, who now sees how the living and the dead are bound by memory and duty. Overcome by the corruption spreading from Reiko, Watanabe takes his own life with a gunshot.
The narrative moves to the burial mound, where Hieda summons the power of a Kojiki incantation to pry open the sealed chamber. Inside, they confront Hiruko in the form of a helmet-like crown, alongside the resting form of Masao’s father. The elder Yabe has transformed into a grotesque, spider-legged creature, a stark sign of the curse’s reach. The escape route is blocked by Reiko and her transformed victims, who stand as guardians of the threshold. Yet the victims unexpectedly allow the protagonists to pass, stepping aside to let them into the sanctum, where Hieda begins the closing rite to seal the gate once more.
Just as the incantation seems to hold, Reiko slips onto Hieda’s back, seizing the chance to coerce him into reopening the passage using memories of his late wife. Masao, who has reclaimed the helmet and recognizes the three-horned crown, completes the counter-spell a second time. This time, Hiruko-possessed Reiko is driven back into the underworld, and the gate is shut again, leaving Masao and Hieda to contemplate the fragile boundary between the living and the dead—and the quiet, costly triumph of sealing away the yōkai once more.
