So I remember this fanfic I read about Onew and an OC back when my account was just a baby. 

So Shinee is thrown back to the Joseon era (it's a historical setting) and they all get new lives. Onew, Key, Minho, and Taemin, are sons of important people and Jonghyun is the son of someone more important, (A leader of some kind). Minho makes a reference to their song Love Like Oxygen to describe how it feels breathing in air that wasn't as polluted as present day Seoul. They try to find their way back but a girl that looks like she recognizes them catches their eye. 

    She is a part of a gang of thieves that plans to steal from (the king or an important figure). Shinee is there and is captured or follows her to the thieve lair. There's this mysterious guy that is always in the shadows. Shinee and the thieves plan to kill/capture/something to the (important figure/king). Shinee kills some people. There is a ion scene (I think) between Shinee because Onew wakes up with a as he was dreaming of the girl and Shinee helps each other get off? So the girl seduces the king/important figure by being a dancer in a circus or entertainment thing. She becomes one of the king's concubines(?) then she sleeps with him and mentions "a part of her died that night" or something along those lines.

    Later a different plan takes place where the thieves become the entertainment and then cause chaos by capturing or killing the king. She is then caught. The mysterious guy from before reveals himself to Onew as the girl before saving herself (the one that got caught). The mystery guy dies. The girl sends Shinee back (I think?) and then she becomes the mystery guy because everything was reset or something.

This was a really important fic to me because it made me get the idea that I wanted to be a writer and I really want to read it again.

Oh yeah there might be something about a museam in there somewhere but I'm not completely sure about it.

Please, Please, Please help me whoever reads this.