This is a story about exorcists and demons. According to legend, a long time ago, the Millennium Earl attempted to occupy the earth, but was eventually destroyed by humans. But the prophet said that the Millennium Earl would attack again. And now, he has come. He deceived those who were lost because of their heartbreak and told them how to revive their loved ones. But what he created was actually a "demon". And the demon is the weapon that the Millennium Earl used to rule the earth. In order to deal with the Millennium Earl and these demons, the exorcists embarked on the road to destroy the demons. They all have their own strengths, and Allen Walker (voiced by Kobayashi Sanae) is one of them. Allen and his friends, including Kanda Yu (voiced by Sakurai Takahiro) and Li Nali (voiced by Ito Shizuka), began to fight the Millennium Earl. This drama is adapted from the manga of the same name serialized in "Shonen Jump" by cartoonist Hoshino Kei.