The main protagonist, Essi is a girl with psychic powers whose mother died under questionable circumstances in an accident ten years ago. Essi's own memory surrounding the event is quite foggy itself; the only thing left behind from that day was a USB-drive disguised as a necklace given to her by her mother, and the recurring dream of a boy named "X". When she is invited to Xen Institute, Essi becomes determined to not only solve the recent murder case, but to finally unlock the secrets of the X-Note, and uncover the mystery of her mother's own mysterious death.