Birthed between Satan and a human priestess, Rin and his brother Yukio are destined for great things and terrible dangers. Enter the school for the exorcists, deepen the bond between the brothers. Your final aim is to create a world where Demons can coexist with humans, so start off in school. Become friends with your classmates, and fight Demons that come across your path together.

[from Blue Exorcist Wiki]