Blue Exorcist - Season 1 - Eps 13: Proof
Shura Kirigakure, a high level Exorcist and former apprentice of Father Shiro was acting as one of Rin's classmates tasked to investigate his connection with Satan. With orders to kill him if it were proven true, she is divided between fulfill her obligations and follow Shiro's request to look after Rin in his place if something would happen with him. Her doubts are cleared when she confronts Rin and finds that Shiro was actually raising him like a son instead of a weapon.
About Blue Exorcist

Title: Blue Exorcist
First Air Date: 2011-04-17
Last Air Date: 2025-03-09
Status: Returning Series
Rating: 7.898/10 (from 460 votes)
Language: JA
Seasons: 6
Total Episodes: 73
Network: MBS TBS CBC Gunma TV Tokyo MX BS11 Tochigi TV i-Television SBS
Genres: Animation, Sci-Fi & Fantasy, Mystery, Action & Adventure
Production Companies: A-1 Pictures, Aniplex, Shueisha, movic, dentsu, MBS
Synopsis
Humans live in the world of Assiah, demons in Gehenna. The two dimensions are not meant to interfere with each other, but demons still possess creatures in Assiah in spite of this. The humans who can fight these demons are known as exorcists. Rin Okumura is a boy who bears the curse of being Satan's illegitimate son. His foster father sacrificed himself to save him from demons. To avenge his foster father's death as well as to prove himself, Rin decides to follow the path of an exorcist and defeat his own father, Satan. To hone his raw skills, Rin enters True Cross Academy to train with other exorcist candidates.
Cast

Hiroshi Kamiya
Mephisto Pheles (voice)