Arca Nova—a land where a massive "magical moon" that once floated in the sky shattered, and its fragments still rain down as meteor showers today. People have developed civilization by mining "Astras," ores born from moon fragments, and utilizing their magical power. On the other hand, the influence of Astras has given birth to ferocious monsters called "Eaters," forcing humanity into a constant struggle for survival.

Magic in this world is not triggered by innate mana, but by using Astras as a catalyst. Astras have attributes: Crimson governs fire and heat, Azure governs water and ice, Emerald governs wind and life, Gold governs light and lightning, and Violet governs gravity and shadow. However, excessive use of power carries the risk of "Astrastone Disease," where the body gradually turns into Astra. Furthermore, blood-attribute magic does not exist in any color of Astra; it is a highly specialized, taboo magic, and therefore extremely powerful.

Eaters are monsters mutated by plants and animals absorbing corrupted Astras. Among them are unique individuals called "Named," who have gained intelligence with a massive Astra as their core. Since Astras can be obtained from monster cores, "Star Hunters," who hunt monsters despite the danger, have become a popular profession.

Major regions include "Valca," a magi-tech superpower that fuses Astras with steam engines; "El Faran," which protects ancient magic centered around a giant World Tree; and the "Ashen Wastes of Oblivion," where the largest fragment of the moon fell. A world where civilization and nature, magic and machinery, and humans and monsters clash—that is the land of falling star fragments, "Arca Nova."