Blue Exorcist or rather Ao no Ekusoshisuto is a serialized anime based on the title manga by Kazue Kato. Currently there is only one season of 25 episodes released.
Okumura Rin and Okumura Yukio were raised by a priest Fujimoto Shiro in seemingly Catholic church with other three clergymen. Although they are identical twins, the character of them were quite the opposite. While Yukio is calm, lovely and hardworking on his studies, Rin is always getting into trouble either on his accords or on others'.
In short, both the Okumura twins are Satan's offsprings, of which Rin was informed by Fujimoto just before his death indirectly by Satan, but apparently only Rin has Satan's demonic power whereas the power "rejected" Yukio. When they leave for a special high school (yes, they are only 15), Rin discovers that Yukio has been able to see the demons wandering around the world and has been being trained to be an Exorcist by Fujimoto since young age. Without a surprise, Yukio is the newly appointed teacher for that year's new Exorcist study freshmen, including Rin.
With the friends from the class Rin and Yukio set out to the journey of avenging their father by killing Satan ("to kich Satan's ass"), therefore ridding the world of the evil.
Personally, I sensed on the cliche Japanese anime style that someone who was "weak" become stronger to "protect the loved ones" in both Rin's and Yukio's character, of which I am totally not that opposed to, because it is motivating after all.
The inclusion both the Catholics and Buddhist are essentially Exorcists (whose HQ is in Vatican, cliche I know) in the face of religion and therefore not that different from each other is amazing, But they forgot to include the other major religion, Islam. I hope they will in the coming seasons, if there is.
The Season One of Blue Exorcist is a perfect piece of Japanese mainstream-battle anime and really entertaining. If you have time and want to spend it watching anime as a distraction for the school break, I will definitely suggest to check this one out.
Simple, doesn't require thinking or solving puzzle, essentially entertaining piece of anime.