Between a recent move to Tokyo and the first day of high school, Rei begins his day weighed down by anxiety and insecurity. His nervousness follows him into the classroom, where, amid the chatter of his peers, Rei is suddenly hit by a strange dream, followed by a pain in his chest. Upon waking, Rei finds a small creature standing on his desk. Dismissing it as part of his dream, Rei heads home. However, to his surprise, he sees numerous other strange creatures of all shapes and sizes roaming the streets, seemingly invisible to everyone else. With countless questions and the small creature from before trailing behind him, Rei's life is changed forever when he encounters a tall, one-eyed figure dressed entirely in black, smiling at him.