She Professed Herself Pupil of the Wise Man Vol. 1

More about the book

The isekai fantasy tale of a young man sucked into another world, where he must roleplay an old man in a young woman's body--which is now an anime from Funimation! (And don't miss the original light novels, also from Seven Seas!) Sakamori Kagami has awakened in the world of Ark Earth Online, a game he plays religiously. The catch? Instead of his normal avatar–an old, bearded sorcerer–he finds himself in the body of a girl! Now he must convince the people of this world that he–she–is a pupil of the legendary wise man who vanished without a trace thirty years ago.