Morale matters just as much as launching a counterassault. Instead of standing on the front lines with the 501st Joint Fighter Wing, the Luminous Witches of the League of Nations Air Force bring smiles to civilians displaced in the human-Neuroi war.

In a prosperous city named Russell City, an omen that threatens to shake its world begins to move within it. A man named Sword is the first to hear the first stirrings of the plot, and throws himself into a shadow war in order to expose it. His only clue is the key word "El Dorado." He meets Sophie, a woman searching for her missing older brother who has only left her with the same words: "El Dorado." With Sword having also lost his younger sister in the past, both are drawn together by the words, and work together to find out its meaning.