Sieg, a court magician assigned to protect a remote frontier town, cannot use magic at all and instead defeats savage magical beasts with his bare hands. The townspeople never see him cast spells and scorn him daily as a useless failure who was banished from the royal capital. When he is suddenly dismissed from his post and expelled from the town despite his successful monster subjugation, Sieg wanders into a rain-soaked forest with nowhere to go. There he encounters a mysterious young woman named Ruruna, who already seems to know him and proposes they travel together to the royal capital.

The story follows Sieg as he journeys across the kingdom with Ruruna, gradually gathering new companions. He is attacked by a hired magic-user named Diboru, who wields magnetism magic, but Sieg defeats him without difficulty. Later, while resting in a cave, he is ambushed by Filim, a succubus who is a natural enemy of mages, yet Sieg overcomes her and eventually recruits her as an ally. Seeking to understand his own power, Sieg travels with Ruruna and Filim to the Great Library of Mujia, where a knowledgeable vampire named Amin explains that Sieg possesses a magic ability called Enhancement. Despised as worthless, Enhancement is actually a very powerful skill that multiplies an ally's strength many times over based on mutual trust. However, the ability also applies to weapons, and Sieg's power is so great that no ordinary weapon can withstand it. Sieg then searches for a blacksmith who can forge a blade strong enough to endure his Enhancement, leading his party into a forest where they are ambushed by a mysterious girl who attacks them with hostility.

Sieg's original frontier town falls to a giant monster after his expulsion, and the creature threatens the entire region. The king eventually reassigns Sieg from border defense to traveling the country solving various problems, beginning with the devastated Garufa territory now menaced by the giant monster that destroyed his old post. Sieg and his companions pursue the monster to stop its advance, gradually confronting larger threats while uncovering the true nature of his enhancement magic and the reasons behind his earlier exile.