Doteihen Reijou ni Hyoui shita 800-nenmae no Akujo wa Hissori Seishun wo Tanoshindeiru.  

The 800-years-old Villainess Who Possessed a Low-Ranking Lady Peacefully Enjoyed Her Youth, ど底辺令嬢に憑依した800年前の悪女はひっそり青春を楽しんでいる。

Nora, who had been sealed for 800 years for threatening to destroy the world, was very bored. One day, she heard the voice of a girl—Cecily—wishing to die, and was awaken. By that time, she'd grown feeble, and her body had shriveled. Thus, Nora proposed to Cecily."If that's the case, would you lend me your body? In exchange, I promise that in a year, you'll have a friend, a lover, a warm family, and promising future prospect for your perfect restart!"The "Incorrigible Villainess," Nora, was resurrected in the body of the "Withered Grass Lady," Cecily.First and foremost, the young lady who had pushed Cecily down the stairs had to be punished. As a matter of course, Nora flatly refused all requests from Cecily's older sister who'd been taking advantage of her for a long time. As for Cecily's family, who had tormented her for not being able to use magic... she'd make them regret! Of course, she also had to enjoy her own school life. Classes, club activities, school festivals. She had to study and play to her heart's content."Let's enjoy the youth that I'd yearned for during my final moments!"This is the story of a young girl who was nicknamed "Withered Grass Lady" as she takes the reins of her youth... and also, the story of a girl touted as the "Incorrigible Villainess" who conquers her fate from 800 years ago, and fulfills all her wishes while doing whatever she wants.(Source: Shousetsuka ni Narou, translated)