Blue Exorcist, Vol. 2 by Kazue Kato

Rin and his exorcist classmates are caught in a secret war against the forces of darkness.

Raised by Father Fujimoto, a famous exorcist, Rin Okumura never knew his real father. One day a fateful argument with Father Fujimoto forces Rin to face a terrible truth—the blood of the demon lord Satan runs in Rin’s veins! Rin swears to defeat Satan, but doing that means entering the mysterious True Cross Academy and becoming an exorcist himself.

Shocked by the death of his foster father and the revelation that his real father is the demon lord Satan, Rin Okumura enters the True Cross Academy to learn to be an exorcist. But every great exorcist has to start somewhere, and for the students of the academy the first step is the Exwire examination. To prepare for the exam, the new pages in Yukio’s class must undergo intensive training. Rin and his classmates have their hands full when a demon appears, but is this a test or something more sinister?