In a world plagued by evil creatures called Shadows, an orphan boy grows up in isolation, locked in the cocoon-like prison of a castle's subterranean cellar. The boy, Ral, has only two companions: Mio, his kind and beautiful tutor, and Grad, the Shadow that lurks inside him. Over time, Ral and Grad form a strong bond. But when the castle is suddenly overrun by Shadows and an all-out war erupts, will Ral and Grad fight on the side of the humans... or the Shadows?
Story by Tsuneo Takano and Art by Takeshi Obata.