In a world that has already been destroyed by death and despair, the legendary Sword God, Karserian Le Vandeiyan, fought until the end. Just as all seemed lost, he is transported to another world—Earth—which has not yet fallen. Monsters are starting to appear, but humanity remains unaware of the looming danger. To prevent history from repeating, the Sword God inhabits the body of a weak human and vows to protect that person's family. With this promise, he prepares to fight once more—and a new story begins.