Takeru is a fifteen-year-old girl raised inside a Buddhist convent, haunted by recurring nightmares tied to a mystical weapon called the Witchblade, sealed somewhere within the temple grounds. When demons resembling figures from Oni folklore attack her home, Takeru becomes the Witchblade's new bearer, awakening a power bound to her family's hidden lineage. Her childhood friend Kou, who descends from a line of demon hunters, and Seishu, a monk who lives at the temple with her, stand by her as she confronts what the weapon has made her responsible for.