Toru, a university student, is invited by his girlfriend Mari to go on a ski trip and stay at the pension "Spool" run by her uncle and his wife Kobayashi in Nagano prefecture. Toru is eager to go on this trip in order to make up for the fact that he and Mari are still friends but not lovers.
While the blizzard is still raging, various people stay at the pension, including part-timers Toshio Kubota and Midori Shinozaki, office workers Kanako, Aki and Keiko, the Kansai boss and his wife Kayama, and freelance photographer Yosuke Mikimoto.
One of the guests, however, is a yakuza-like man, Ichiro Tanaka, who wears sunglasses and avoids being seen.
After dinner, a letter is found in the room of the three office workers, which says "Tonight, 12 o'clock, someone will die", which is dismissed as a prank. After nine o'clock at night, they hear the sound of breaking glass from upstairs, so they investigate the rooms upstairs and find a dismembered corpse in Tanaka's room. The window of the room is still broken and open, and there is no sign of the murderer.
There was no sign of the killer. A blizzard prevented anyone from getting out, and everyone was completely trapped. With the phone lines cut and mobile phones out of range, it is a closed circle where the police cannot be called. Is this murder the work of the local yokai, Kamai-tachi? The protagonists are threatened by the invisible shadow of the killer. As if to mock them, a second and a third murder occur.
In order to protect his beloved Mari, Toru sets out to find the true culprit in order to solve the case.