A village divided by a river is a village hiding something. Hiroshi arrives as the outsider who sees what everyone else learned to stop asking about, and the show knows that curiosity in a place designed to punish it is its own kind of trap. The horror isn't jump scares or gore; it's the slow realization that the friendliest people in town are the ones most likely to drag you across that river. Twelve episodes to figure out if he belongs there or if belonging was always the point.

Hiroshi Kuzumi, a teenager, relocates with his family to Jogamachi, a mountain town because of his father's work. A river splits the town into an old quarter and a new one, and many strange local customs have survived there. At school most of his classmates embrace him eagerly, and he soon befriends his clingy neighbor Isuzu Tsumuhana and Kaname Asagiri, another recent arrival. The distant class president, Nemuru Kushinada, keeps apart from him and tells him only to avoid the old streets. Then townspeople begin to vanish, explained away as moves or transfers, while masked figures led by a scythe-wielding girl hunt through the dark streets beneath a red moon. Based on a visual novel, the show is a supernatural mystery with strong horror elements.