In an era where one in every twenty people awakens to a "special ability," Hiroto Takigami is a weak ability user who can only communicate with spirits. However, for some reason, his stepsister Rei, the most powerful ability user, harbors deep hatred toward him. The moment he graduates from an ability training institution and gains full control over his power, Rei kills him. With only one year left to live—his "remaining lifespan" set—Hiroto falls into despair. Just then, a certain spirit appears before him, revealing an unexpected secret about his ability...