You can now watch the Son of Satan on the Funimation Now service as Blue Exorcist and Blue Exorcist: Kyoto Saga joins their huge streaming library as of yesterday. Both series are available in either Japanese with subtitles or dubbed in English.
Rin Okumura, and his younger brother, Yukio, have joined the renowned True Cross Academy in hopes of becoming exorcists to protect their world from the dark forces of the demon world. Rin possesses the power of Satan, which manifests into blue flames that can destroy anything in their reach; only are they kept in check with the sword he carries at all times. Rin is kept on his path to protect the world and the ones he loves with support from his brother and friends at the school.
The Blue Exorcist anime is based upon the manga of the same name by Kazue Kato, which is published in North America by Viz Media. A film, Blue Exorcist: The Movie, was released in Japan on December 28th, 2012.