In a world where magic is both feared and coveted, mages are hunted by knight orders while magears—powerful magical artifacts implanted in the body—offer immense power at the cost of the user's life force. The story follows Gar, a pragmatic young mercenary who trusts only his sword and scorns magic. As a child, he was saved from a fatal wound by a mysterious archmage who gave him a magear, Gusion's Emerald, embedded in his right eye. Years later, Gar accepts a job to accompany a knight order tasked with hunting a rogue sorcerer who has stolen a magear. When the knights are ambushed, Gar discovers the sorcerer is none other than Kuon, the very archmage who saved him. Kuon defeats the knights effortlessly, then saves Gar again by transplanting his own magear into Gar's eye, warning that using it will steadily drain his life. Kuon then insists on taking Gar as her apprentice, a proposal Gar resists because he has no interest in magic. But after being forced to accept, the two begin traveling together.

Gar, a realist who relies on his sword and physical prowess, gradually learns to control his magear and practice magic under Kuon's eccentric teaching. Kuon is a youthful-looking, centuries-old archmage of immense power who uses illusion and transformation magic. She is strict yet caring, and her reasons for choosing Gar remain partly hidden. Their journey expands when they encounter Zaza, a beastman mercenary who becomes a close friend and rival, and then join forces to rescue a girl named Jinza from the slave trader Caja Salam. This leads to a shipboard battle against the lion‑man Dares, where Gar learns to combine his sword skills with basic elemental magic. Later, a prophecy warns that the city of Astol will suffer a catastrophic massacre. Gar and Kuon, now cooperating with Prince Leon and his aide Luka, prepare for a showdown with Caja. The story develops into a large-scale magical conflict involving golems, ancient ruins, and political intrigue. Key arcs include Gar's reluctant magical training (starting with learning to extinguish fire rather than create it), his growing mastery over the Gusion's Emerald despite the physical toll, and the gradual revelation of Kuon's deeper plans. Along the way, Gar transforms from a loner into a leader of a small band, while the bond between master and apprentice deepens beyond mere duty.