She Professed Herself Pupil of the Wise Man: Mariana no Touki Hi

She Professed Herself Pupil of the Wise Man (賢者の弟子を名乗る賢者 〜マリアナの遠き日〜, Kenja no Deshi o Nanoru Kenja: Mariana no Touki Hi) is a Japanese manga series by Vanilla Boww based on the light novel of the same name by Hirotsugu Ryusen and Fuzichoco.

Plot
Sakimori Kagami has woken up in the world of Arch Earth Online, a VRMMORPG he's been playing intensely for a long time. The catch? He made some adjustments to his character when he last logged on, which he thought he hadn't saved. Instead of his normal avatar of an old, bearded sorcerer, he's in the body of a young woman! Now he must convince the people of this world that he–she–is a pupil of the wise man who vanished without a trace thirty years ago.