A school fantasy about Sein, a boy chosen as a holy knight who nevertheless wants to become a dark knight, causing trouble at a foreign academy with his attendant Melia. His misguided efforts, despite having only light magic, lead to dungeon exploration and new companions.

A boy with only the power of light charges headlong down the wrong road toward becoming a dark knight.

A light novel project recognized with an Encouragement Prize at the 11th HJ Bunko Awards. It is recorded as a fantasy premise that shifts the usual hero-and-demon-king structure through the role of a gatekeeper.

The story of hero and demon king is reframed through the one who guards the gate.