To fight the increasing number of worldwide terrorist groups and psychopaths, the confederation proposed to have 242 countries hold hands and establishing an organization of geniuses, with at least a score of 180 IQ, with unique skills.

This is "SI", also known as the "Special crime Investigation".

Aym is a slave who is descended from a a powerful witch. Because of this, his blood has the power to attract demons and he is used by his master to summon them. Just when Aym accepts his cruel fate, the sudden appearance of a group of magicians with the ability to defeat demons might be opening up another path for him.