In 2045, singing is banned. Humans no longer create or perform music; instead, an app called MiucS generates all songs for them. One day, Seria Aiba hears a human singing voice while out with friends—something that should not exist. Following the sound, she encounters a mysterious presence: a ghost. What appears before her is not an ordinary spirit, but a figure from beyond this world known as a Great Ghost. As Seria gets drawn into encounters involving Great Ghosts, the psychic organization TERA, and a strange song called the Possession Requiem, she steps into a hidden side of a world that has erased human music. This is the story of how Seria's life begins to change—and the path that leads her toward becoming a ghost herself.