One day, high school student Akihito Kanbara instinctively goes to save his fellow schoolmate, Mirai Kuriyama, from committing suicide. Following his pleas, Mirai suddenly stabs Akihito with a sword formed out of her own blood and is shocked to discover that Akihito is an immortal "half-youmu"—the offspring of a supernatural creature called a youmu and a human. After learning that Mirai is a Spirit World Warrior —specialists who protect humans from being affected by…