Ao no Exorcist is about twin brothers, one of whom happens to be the son of Satan. Okumura Rin and Okumura Yukio are twins who are orphaned very young and raised by a guardian exorcist, Fujimoto Shiro. Rin is a misfit who is clumsy, gets into trouble nearly constantly and can’t even manage to keep a tidy appearance. Yukio is the perfect son, who is following in his father’s footsteps and has trained to become an exorcist. Both boys love their “father” and care about each other. During the first episode, Shiro is killed by Satan. It comes out that Rin is actually Satan’s son, and he comes into possession of a powerful magic sword, as well as some serious powers of his own. Rin vows to become an exorcist and fight Satan, who killed his “father”.
Needless to say, for the son of Satan to become an Exorcist is not well received in many quarters. Rin and Yukio move into the Exorcist school, where Yukio already teaches as a full exorcist. They attempt to keep Rin’s parentage and demon capabilities secret from the other students although the instructors know about it. This attempt to hide Rin’s true nature is hampered by the fact that he has a tail. Rin meets and begins to form friendships with the other exorcist-wannabe students, including a girl named Shiemi who has healing powers and who stands by Rin even after she finds out he’s the Devil’s son. Rin’s interactions with the other students are not smooth from the beginning, as he continues to be something of a screw up, and they get significantly worse as his true nature becomes known.
All members of the church are also not happy with Rin’s presence as an exorcist in training. Shura is a church exorcist who tries to help and support Rin along the way. Arthur, the Paladin or top exorcist, is decidedly against Rin’s presence at the school and against him becoming an exorcist. In addition, the machinations of the school’s headmaster, Mephisto, who is himself a demon, are not clear along the way. At one point Rin loses control and is captured by Arthur and held in stasis by the church while his brother and his fellow students work to find a way to free him.
Toward the end of the series it becomes apparent that Yukio has the same parentage as Rin, and Yukio and his demon powers are manipulated by Satan to create a gateway into the world to destroy the church and rule the world. In the end everyone works together and Rin and Yukio combine their massive powers in order to destroy Satan’s gate and save their friends and their world.
This is pretty much an awesome series. The characters are fun and easy to like and follow. The plot is fairly unique, with Satan’s son studying to become an exorcist. The music is exceptional. I especially liked the Ending theme song, “Wired Life”, but it’s all great. Basically, I recommend you watch this series. It’s worth it.