The Exwires are tasked to look for the ghost of a child that is haunting Mephisto Pheles' amusement park. Rin and Shiemi manage to find the ghost first, but Shiemi ends up chasing it by herself while Amaimon, a higher demon and another son of Satan, steals Rin's sword and forces Rin to fight with him. Mean while another exorcist comes to defend him, and it is reveal to be an old friend of Rin's brother.

The first semester has ended, signaling the start of summer vacation for True Cross Academy students. But there’s no rest in sight for Rin and the other ExWires: first they must take part in a 3-day drill to prepare them for actual combat, under the guise of a camping trip out in the forest.

Rin and his classmates succeed at the task gave to them by their teachers, but the camp is attacked by Amaimon, who holds Shiemi hostage to force Rin to fight. Having no option but to go full force against Amaimon, Rin is forced to reveal his secret by exposing his true form in front of his friends. With the other Exwires fleeing astonished after learning the truth about him, Rin easily overpowers Amaimon, but loses control of his flames and goes on a rampage. The Demon-Slaying Blade is cracked in the process.

The Exwires learn that Kamiki's birthday is coming and they decide to make a surprise party to her. Despite all their efforts to make the party a secret, Kamiki ends up figuring the truth and claims that it should also be dedicated to those whose birthday already passed too. In the end, the party becomes a celebration to everyone's friendship.