Episode 85

The Evil Within Demon's Head Castle is the eighty-fifth episode of the InuYasha anime.

Synopsis

 * 1) Inuyasha and his friends meet an old exorcist and she tells them of the curse of the demon's head castle, where the head of a demon was supposedly buried underneath.
 * 2) They all go to the castle to investigate, and find that the lord has likely been possessed; they learn that a massive demonic aura is surrounding the castle, though the exorcist is unable to sense it.
 * 3) Many monks and priestesses have tried to exorcise the demon before, but with no success.
 * 4) The princess of the castle takes Miroku down to where the demon's head had been buried; it is revealed that she is actually the demon, and lured him down there to devour him.

Summary
Inuyasha and his friends run into an old woman, Haori, fighting a demon and save her. After she introduces herself as a demon exorcist, they decide to join her to fight an oni haunting a nearby village.