This Drama ended getting 8/10 from me for surprising me in positive ways more than once.

First, it COMPLETELY threw me as to who the killer was, I did not see that coming at all - excellent!

Second, the tone ended up being rather unexpected, another pleasant surprise

Third, it's handlnig of the characters showed intelligence. There was nuuance and context for the characters' behaviour, and the final end of some characters' arcs was balanced and realistic. Not implausibly rosy or even implausibly complete. A great example was the resolution of the ML's own mother issues, the end to that arc was note perfect.