The World of Ao no Exorcist is the main setting of the series. While the series is set in modern times, the story places our world next to a parallel world: Assiah, the human world, is connected to Gehenna, the Demon world.
MashōMashō (魔傷?), or Temptaint, refers to wounds or illnesses that are inflicted by a Demon. Once a person sustains a mashō, they become able to see Demons for the rest of their life. As such, it is a rite that all prospective Exorcists must go through, if they had not done so incidentally prior to becoming an Exorcist. Evidently, Rin did not have to undergo mashō because of his Demon heritage.
In the anime "Mashō" was renamed "Spirit Wound".
- The demon world Gehenna is likely based on Gehenna from the Hebrew Bible.
- Gehenna is also seen as the Seventh Hell.