Blue Exorcist (3): Symbols and Myths
In the anime blue flames were a sure fire way to know if someone or something was associated with Satan. Blue flames obviously representing Satan and great evil, being that many people associate blue flames not only with Satan but with death as well being that on one night an entire temple of priests were murdered by those blue flames.
This is the Emblem of the True Cross Order given to trainees of the Order when they become full fledged exorcist this represents an individuals ability to exterminate demons in any form.
Mephistopheles is a demon from German folklore who originally appeared in literature as the demon Faust.
In the Anime Mephisto is in fact depicted as a demon, as revealed by little hints throughout the anime and then outright stated during a moment he was believed to be exhibiting shady behavior. Also in the anime he seems to have the capability of controlling time.
Blue exorcist has connections to Japanese culture but not really any references to Japanese civilization.
After nine years of education you get the choice of if you want to continue on with your education. It is at the beginning of the series that Rin is at this point in time and deciding whether or not he wants to continue with school (which he doesn't) or go into the work force (which he does).