Rin and Kamiki are attacked by an unknown enemy and Mephisto Pheles orders the Exwires to check the barriers protecting the school looking for any breach. The enemy is revealed to be a demon who took advantage of Konekomaru's fears to infiltrate the Academy. Meanwhile, Shura locates a hidden door leading to a suspicious abandoned lab. When Konekomaru's heart succumbs to the demon, his friends rush to help him, and Rin manages to slay the monster and save his life. Ashamed of causing so much trouble, Konekomaru decides to leave the Academy and return home, but Rin and the rest of his friends reach him before he departs and convince him to stay.

Rin and his companions manage to flee from Satan who starts destroying the True Cross Academy with his flames. Knowing that Satan still stands beside the Gate because Rin has the power to destroy it, Shura comes up with a plan to distract him to give Rin an opening to do it, while the other students help evacuate the school. Their plan fails when Shiemi intervenes trying to dissuade Yukio with no success, but Rin manages to have his brother regain conscience and expel Satan from his body. However, the gate keeps getting stronger and it will not be long for Gehenna and Assiah to merge into one single realm.