Tom, a high school student, finds a strange picture book in a park near his home. When he turns to a forbidden page, he is suddenly drawn into the world of the book. There, he meets Rena—his childhood friend and classmate—who had mysteriously gone missing. As they begin to explore this strange world, they accidentally uncover its hidden secrets and find themselves being chased by a mysterious man. Soon, they lose their memories and are thrown into another realm: the Mirror World. In this parallel world, Tom starts recovering fragments of his memory and slowly learns a terrifying truth that goes beyond time and space.