Based on the manga from Yun Kouga, creator of the beloved manga Loveless, Riddle Story of Devil sends twelve female assassins to a prestigious boarding school to compete against each other in a secret killing game. The winner will be granted anything her heart desires, but only one girl can come out on top. The mission is simple: send fellow student Haru Ichinose to an early grave. The task should be easy for heartless assassin, Toukaku Azuma but everything changes when she finds herself strangely drawn to her naive target. Her decision to use her lethal skills to keep her new friend alive will raise the stakes of the game and push the girls closer together as the other beauties threaten to tear them apart.