For five centuries, Arthur Gaz, also known as the Taboo Emperor, ruled the Gaz Empire with an iron fist, subjecting his own people to inhumane experimentation and committing atrocities. However, five years ago, the Eight Heroes rose up and defeated him, finally putting an end to his 300-year-long war against the alliance of six countries. Tooru Acura, a former saboteur struggling to find his place in the new world order, is approached by Chaika Trabant, a white-haired wizard. Chaika is searching for the scattered remains of her father, Emperor Gaz, so she can properly bury him. She enlists the help of Tooru and his sister Akari on this quest. However, the Council of Six Nations, formed by the alliance that defeated the Gaz Empire, dispatches agents from the Kleeman Agency, led by Albéric Gillette, to capture Chaika. As the truth about Chaika's identity as the daughter of Emperor Gaz is revealed, the Acura siblings are forced to make a difficult decision. They must choose between helping Chaika find closure or preserving the fragile peace that has finally been established in the continent.