Best drama so far

First episode was boring, so i almost dropped it, but it kept getting better and better. With each episode, more characters were revealed and the story would become more complicated. Every new person brings new problems. Acting was also normal, it wasn't exaggerated like in other dramas, which I liked the most. I also liked character developments, especially for their children. I never expected this would happen at the end. The best plot twist ever. I just hope that one person stays alive :'(