Mabeopsaga Jugeumeul Majihaneun Bangbeop

For the past 300 years, Ente has fought against the dragon, Caliesto, as the reigning Magnus. When she finally slays her nemesis, she welcomes death with open arms, hoping to meet her beloved teacher in the afterlife. But instead of finally gaining the eternal rest she has long yearned for, she opens her eyes in the body of Melissa Tiony, the richest bachelorette in the empire. Ente realizes that her lifelong mission has yet to be fulfilled, as it is impossible for her to die so long as Caliesto still breathes. She must find a way to regain her magic and finish him once and for all, and the first step to doing so is attending the Academy of Magic in the city of Kastium. Ente sets out on another journey, hoping that this one will be her last.

(Source: Tappytoon)