Kurenai Gekkou, a freshman and also the student council president of Miyasaka High, is a self-proclaimed genius. Nine years ago before the starting timeline of the story, due to a certain deed committed by his younger twin brother, Hinata, Gekkou was prompted to constantly seek out power, initially driven by the fear for his life, and later motivated by the prospects of revenge.

Gekkou is demonstrated to be quick-witted and highly intelligent. He wields an ancient fencing-like sword known as Spell Error, and is trained in several traditional arts of exorcism. As the student council president, he has made a contract with and is tasked to be guardian of the Holy Ground, a location with certain special properties over which Miyasaka High was built.