"I've come to eat you." Shiori, a mermaid girl who suddenly appears, takes the hand of Hinako, a girl living alone in a seaside town, and speaks these gentle words. Hinako's flesh and blood is said to be exceptionally delicious—so much so that it attracts countless supernatural beings (yokai). Shiori promises to protect Hinako until she has matured to perfection, vowing that one day, she herself will be the one to devour her. A desperate hope springs forth in Hinako's heart— "Perhaps this person might be able to grant my wish."