I haven't seen any of this series but considered adding to my plan to watch list. My first thought when i read this review was "could his his sister actually be the monster?"
I actually think this series is really overhyped and the story itself was somewhat mediocre. The production and acting were both very good to excellent. I think there are other series that are far more deserving of more attention. However, it's good to see a kdrama doing so well internationally. Also, great job on this article.