Ao No Exorcist

Rin is enrolled at True Cross Academy's exorcist cram school by Mephisto, the academy's chairman. He is shocked to learn that Yukio is one of his teachers, having already been a prodigiously graduated Exorcist. Yukio had always been aware that Rin was a demon. Rin demands to know why Yukio kept this a secret, and Yukio says he blames Rin for Shiro's death. After Rin protects Yukio from a hobgoblin, Yukio recalls Shiro telling him to protect his brother, which motivated him to become an Exorcist.