Blue Exorcist is an ongoing anime series that started in 2011. So far 37 episodes of Blue Exorcist have been aired. With a total of 10 reported filler episodes, Blue Exorcist has a moderate filler percentage of 27%. Assiah, the realm of humans, and Gehenna, the realm of demons. Normally, these two dimensions would never intersect, but the demons are now intruding on the material world.