Ajin boys who show signs of special abilities are conscripted to serve in the imperial palace as beast-servants--status symbols and shields for their royal masters, to be kept or discarded on a whim. When they were children, Rangetsu's twin brother Sogetsu was ripped from her arms and sent to the palace to attend Prince Tenyou as a beast-servant, where he quickly fell victim to bloody dynastic intrigues. Now in a world that promises only bitterness, Rangetsu's one hope at avenging her brother is to disguise herself as a man and find a way into the palace!

Sogetsu may have been released from the emperor's cruelty, but he's not yet completely free of his ordeal. In order to survive the experiments he suffered through, Sogetsu's mind splintered into many personalities...and only one of them made it out of the inner palace. Now he is racked with guilt over being the wrong Sogetsu, and the agony of feeling unworthy of being rescued is pushing him into unexpected action!