In a world of islands floating in the sky, the horned boy Seth is known as one of the “infected”, a sorcerer feared by the very people he protects. Creatures called Nemeses fall from the clouds, and only those like him who have survived their touch can fight back using the power of Fantasia. To the fearful populace, he is a walking calamity, a monster magnet just as dangerous as the beasts he hunts. Yet, he clings to a secret, near-mythical quest: to find the Radiant, the fabled nest of the Nemeses, and destroy it once and for all.

His days are a balance of volatile power and simple duty, living under the stern guardianship of his mentor, Alma, who tasks him with controlling the chaotic magic raging within him. This struggle to master his own strength is a constant, quiet battle, often complicated by the distrust of his neighbors. The air grows heavier, however, with whispers that an Inquisitor has been seen patrolling the nearby skies, a familiar face from a past encounter that promises new trouble.