Konyaku Hakisarete Shoukan ni Urareru (Yotei) nano de, Choukoukyuu Shoufu wo Mezashimasu!

The protagonist suddenly realizes she’s been reincarnated as Natasha, the villainess of a novel! If the story follows its original course, her fiancé will break off their engagement and she’ll be sent to a brothel. …Even though she’s terrified, this fate seems impossible to escape. “In that case… I might as well become a high-class courtesan!” Determined to face the doom ahead, Natasha devotes herself to polishing her manners, education, and artistic skills. The only thing she’s still missing is actual experience. And when she finally heads to the brothel, waiting for her is the owner who begins giving her seductive “night lessons”! His gentle instruction sends her heart racing nonstop… The beginning of an unexpected romance! https://www.cmoa.jp/title/332907/