A force known as Astral power is wielded by astral mages. Fearing its destructive power, the "Empire" persecutes those who show their abilities. The tormented mages then founded the Nebulis Sovereignty to flee from their oppressors. Since then, the two nations have been in bitter conflict, the war still going strong for more than a century. After committing the great crime of freeing an imprisoned witch, the talented knight Iska is sentenced to prison. A year later, the Empire leadership suddenly decides to set him free, with the condition that he hunts down a fearsome mage known as the "Ice Calamity Witch." Hoping to end the war, Iska agrees. Coincidentally, the Ice Calamity Witch herself, Aliceliese "Alice" Lou Nebulis XI, also wishes for peace and is willing to do everything she can to bring down the Empire. As Iska and Alice both yearn for a crusade that will turn the world into one without struggle, woe, or pain, the strings of fate tie them ever closer together.

Over a century ago, astral mages under persecution from the Empire banded together and established the Nebulis Sovereignty under three founding families: Lou, Hydra, and Zoa. With the leadership of Millavair Lou Nebulis VIII, the Sovereignty aims to minimize casualties in their conflict with the Empire—a stance the extremist Zoas disagree with. Tensions rise between the families as the upcoming election to decide the next leader approaches. The Zoas are willing to do anything to achieve success; however, a world-ending war may ensue should they be victorious. Princess Aliceliese "Alice" Lou Nebulis XI has no choice but to cooperate with any potential allies in order to advance towards her ultimate goal of ending the conflict that has long tormented everyone involved. This includes Iska—one of the Empire's greatest warriors and her greatest rival.