It was that day when Rin and Yukio fought against Satan. It was that day when Yukio awoken his demonic powers. It was that day when Satan's reign was put to an end. Months after the Okumura brothers had placed the threat in his place, it was back to Cram school. Guard was kept high for anything that could be thrown at them... Until a pack of demons attack the school to retaliate against the fraternal twins who defeated Satan. The students are quick to put what they learned in action. But they didn't expect their own teacher to forget the most important thing about what was summoned within him.