Wether you like Ao no Exorcist or not, wether you find it original or cliche’d, the one thing you can’t take out in this series is the coolness factor of Rin’s flames. You’d be blind if you didn’t go “Hah. That’s awesome” when you see Rin’s power. The blue-ness of it is very appealing to the eyes.
Enough about Rin’s power. This episode was amazing in epic proportions. Unlike the Hanairo who’s fairly inconsistent, Ao no exorcist just keeps getting better and better. You just know this series is character driven when someone’s fighting and the series keep on showing the different characters, how they would react and even Rin himself, with his purpose in fighting. It’s already cool but it also has depth. That’s the thing Ao no Exorcist thrives on.
Also Mephisto was extra cool this episode, sitting drinking tea while Rin is fighting. He also said some lines which somehow foreshadows what could happen in the next few episodes.