In a world where every person possesses an elemental affinity for earth, water, fire, or wind, magical beasts periodically emerge to threaten society. To counter these threats, those with especially high magical power are organized into special defense units known as the Magie Legion, or Magi for short. This system extends to high schools, where the most gifted students are chosen to form elite squads based at a central headquarters called Cartier. Each squad is led by a Master, typically a third-year student, who selects a second-year assistant called a Sweet to serve as their partner. The Master and Sweet work in tandem, summoning enchanted tools called items with their magic to fight the beasts.

One day, a girl named Sei transfers to the Kinjakushi Magic Academy. No sooner has she arrived than she is unexpectedly chosen as the Ref Sweet, the assistant to the school’s top magic user, a gifted and diligent student named Ryoka. For Sei, who can barely use magic at all, this appointment is a life‑or‑death predicament. With the help of an enigmatic creature named Unyu, she manages to scrape together enough magical ability to perform basic spells, but her position as Ref Sweet remains precarious. The story follows Sei’s struggles to master her latent powers, navigate her duties as Ryoka’s partner, and maintain her place in the Magie Legion, all while the bond between the two girls gradually deepens from initial friction into a close friendship. The manga spans four volumes, tracing Sei’s growth as a magic user and the pair’s involvement in the school’s defense activities against the recurring beast threats.