This drama is actually good in the first few episodes because it gives the implication that there's a lot to uncover. It keeps driving you in deeper, introducing new characters now and then, but in the end, that's all you get. The actual point of the story is a mystery, the story itself is a mystery, and the characters are mysterious.

The creators of this show are trying to fill a book with the solution of a 1 + 1 equation. They manage to have nothing original, plot holes at the most crucial points, a bunch of absolutely useless characters, and even fail to present the show coherently with their confusing timelines. These timelines have absolutely zero relation or connection, and they switch between them without any information to the point that one will only realize they are distinct in the future.

They only managed to expose Go Min Si pointlessly and for absolutely no reason other than to maybe have a point of watching. She killed it, and she may be the reason to make you thrilled for the story, but from the moment she appears to the end, there's nothing else to her character except confusion and mystery.