Silent Witch: Chinmoku no Majo no Kakushigoto - Sennyuu Kiroku

Monica Everett, the Silent Witch, is one of the Seven Sages, the highest sorcerer. She is painfully shy and nervous around others, so she secludes herself deep in the mountains with her black cat familiar. She one day receives a top-secret mission to go undercover at Serendia Academy, a prestigious school for nobles, and guard the second prince. What awaited her after sneaking into the academy was... Let us revisit Monica's report of going undercover.

(Source: Crunchyroll)