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.

As his vision of the past draws to a close, an older Rin bears witness to the tragic climax of the Blue Night. He watches as Satan's cloned body can no longer contain the massive cosmic energies within him. The Knights of the True Cross are faced with an unprecedented crisis as a wave of destruction begins to sweep across the world. Although just a newborn, Rin is hugely powerful and his demon heart scourges the Knights of the True Cross with its fire. The blue flames continue to spread, and no one will be spared their heat...