世界を司る女神から溺愛されるセインは、史上最強の聖騎士として崇められながらも、とある理由から暗黒騎士を目指している。闇魔法を修得するため、身分を隠して他国の魔法学園に入学したところ、自作の黒ずくめの改造制服が悪目立ちして変質者扱いされた上に、闇魔法の適性が皆無なため落ちこぼれの烙印まで押されてしまって――。

Young Sain Forth has it made; as the famed Holy Knight, he has the people’s love, the respect of kings, and the blessings of a literal goddess. His aspirations lie elsewhere, though. With his assistant Melia at his side, he leaves for an academy in a foreign kingdom, where he is treated as a deviant by his peers. It’s his own fault, mind you—his stubborn insistance on wearing a custom, all-black uniform makes him stick out. He isn’t the only outcast in his class: Alicia, born into the Clan of Light but unable to use anything but fire magic, faces similar struggles, and the two quickly become allies. Alicia proposes that they enter the labyrinth below the school in search of a holy sword, but Sain has other plans in mind: a doom sword. And so, with his friends in tow, Sain ventures into the perilous unknown, driven by a wish to become the coolest, edgiest, most awesome thing in existence: a Dark Knight. There’s just one problem. He can’t use dark magic. Like, at all.