Kazuya Kujou is an international student at Saint Marguerite Academy, an opulent boarding school located in the Southern European nation of Sauville. Hailing from Japan, his jet-black hair and dark brown eyes lead his classmates to ostracize him, earning him the moniker "Black Reaper"—a reference to a widespread urban legend concerning a traveler who brings death in the spring. On an ordinary day, Kujou heads to the school's lavish library to look for ghost stories. Yet, his attention soon shifts when he notices a single strand of golden hair on the stairs. Following the steps, he arrives at a vast garden and encounters Victorique de Blois, a striking, doll-like girl whose intricate and imaginative foresight enables her to predict their futures, which are now intertwined. As further mysteries rapidly unfold—such as the sighting of a ghost ship and the presence of an alchemist possessing transmutation powers—Victorique and Kujou, linked by fate and their distinct abilities, find themselves compelled to depend on one another.