In this kingdom, Ajin are considered no better than beasts. The men are sent to war, the women serve in brothels. Those who are lucky enough to live to old age spend their last years doing degrading, menial work. Boys who show signs of magical ability must serve the imperial family in the palace. Rangetsu's twin brother is sent to the palace to serve the Prince Tenyou, but he only lasts a short time before he is murdered. Rumors say his master was the one who aimed the blade, and Rangetsu decides to puts aside her femaleness in order seek revenge.