Blue Exorcist, Vol. 4

Kato, Kazue. Blue Exorcist, Vol. 4. 2011. 186p. ISBN 978-1-42154047-4. Available in the graphic novels section of the library. 

The story ended in Blue Exorcist, Vol. 3 at camp, where the exwires were tasked to capture a lantern in the woods and bring it back to camp. when When Konekumaru discovers that the lantern is in fact the size of a horse-drawn cart, he enlists Rin and the rest of his friends. Suguro realizes that the rules were not that they all had to capture a lantern by themselves, but rather that they were to collaborate together. Sugaru comes up with a clever plan to move the lantern and get it across a rope bridge, but at the same time he remains suspicious of the blue light he saw in the woods next to Rin earlier that evening.

Mephisto Pheles releases Amaimon, forcing Rin to join the fight after Amaimon kidnaps Shiemi. Shura gives Rin his sword back, and he reveals his true nature to his friends. They are shocked that the son of Satan has been with them this whole time, and Shiemi takes it especially hard.

Meanwhile, the Vatican sends the Angel to discover why Shura has not completed her own investigation. Rin is brought to the Vatican's court for possible execution, but Mephisto convinces the court that for the time being Rin should continue to train so he can become the church's strongest weapon against the devil. Yukio and Shura will personally oversee his training, which will cause sparks among the former classmates ...