In the Royal Magic Academy, a special program class is thrown into disarray by the arrival of a new instructor named Setsuna. He possesses a glaring flaw for a magic teacher: he cannot activate magic himself. Assigned to supervise four exceptional yet problematic students, Setsuna is immediately met with disdain and disappointment from the prodigies who expected a master of the arcane arts.

The conflict ignites when one of his students, Serra, a proud vampire whose quiet anger boils beneath the surface, challenges him to a duel. Fueled by the indignity of being taught by what she perceives as an incompetent, she aims to force his retirement. However, Setsuna responds not with a typical magical demonstration but with an audacious and terrifying counter-proposal. He invites not just Serra, but all four special students to attack him simultaneously, declaring that if he defeats them, they will be bound to him as slaves.

This act reveals Setsuna to be a brutal, unorthodox "demon instructor." His guidance seems to embody all the torment in the world, as he wields a perverted and astonishing form of combat that mocks the very essence of traditional magic. While on the surface he appears to be a sadistic brute who toys with geniuses, his true purpose for this cruel methodology begins to hint at a deeper, hidden objective behind his teaching methods. The story follows this powerless yet overwhelmingly dominant instructor as he breaks down and rebuilds the elite students through sheer terror and unorthodox discipline.