This TV series has a similar plot to the movie"While you were Sleeping". If you try to compare the two then you could find the mother in LS annoying. Because she is always finding fault with the second child . But overall I think the series is really well done. If you liked "While you were sleeping." There is a good chance you will like this.

On the surface this is about mistaken identities and how one good deed can sometimes be misconstrued. You can get stuck in an unintentional lie that was was told with good intentions. I like how it showed the development of the main characters.
I like the realism of this series and the attention to small details. I like how they have emphasized the loneliness between the characters. There is more depth to the story then in typical Lakorns and I like how they do the flash backs. There were more issues than just loneliness. That's all I am going to say so I don't spoil it.

Update: the story is taking a darker turn. It still is good but no longer the light hearted comedy it started out. I just hope it doesn't get too dark.

Update 2: I just finished the series. It was really good. I like the twists in episode 13 and 14. I love the character development and redemption and the clear happy ending.