Ao No Exorcist Episode 20 -

In Blue Exorcist episode 20, "Mask," Rin and Yukio return to their childhood home to confront a mysterious attacker, beginning an anime-exclusive filler arc. The plot follows the brothers investigating a masked figure attacking the Southern Cross Monastery and, specifically, those related to Satan. Ultimately, Rin must control his blue flames to defeat the culprit, who is revealed to be the reanimated body of Michelle, the wife of a teacher at the school.

You can find more detailed information and recaps for the episode on the Ao no Exorcist Wiki and Rotten Tomatoes . Episode 20 | Ao no Exorcist Wiki | Fandom Ao no Exorcist Episode 20