The Hidden Eldest (Welcome To Demon School AU)

Kim Y/N, the most professional Doctor in any kind of surgery have a very very shocking past.
Her past includes Kidnapped by lots of Mafia and one day after they beat her badly, they left her passed out inside in Gonjiam the haunted asylum. They thought she's dead but unfortunately the creature took care of her for a while then decided to give to a Demon, Sullivan because those Mafia faked being police just to check whether the little is already dead or not. For Y/N's 3 years life with her 'grandfather' she never seen other demon till now except for her grandfather and one of her best friend, Momonoki who's a demon herself. After Y/N's family told Sullivan that the line is clear, Sullivan couldn't help but to cry because after all these years he felt alive but his cries stopped when Y/N's family told him he can came to human world to meet Y/N as much as he like which Sullivan totally agreed.

Y/N will finally go back to the home where she loved to be and always missed there.