Brash single mother Nikuko is well-known for her bold spirit, much to the embarrassment of Kikuko, her pensive yet imaginative daughter. In contrast to her mother, Kikuko wants nothing more than to fit in as she navigates the everyday social dramas of middle school. Life in the harbor is peaceful until a shocking revelation from the past threatens to uproot the pair's tender relationship.

YouTuber Tomoki Uchikawa, along with his friends Hinako, Souta, and Nanae, head to the former Ishio Village, where there are rumors of people being spirited away, to film a video investigating urban legends. However, their whereabouts remain unknown, and the police discover the rental car they had rented near a tunnel on the outskirts of the village. The video cameras left behind there show shocking images of locked houses, children in armed uniforms, imprisoned adults, and adults being infected by a strange disease, a rotten demon, that occurs on the night of a new moon.