I was hesitant to watch this first because I read reviews/comments from a couple of people said they got bored, it got draggy, or the leads don't have chemistry. Some people were worried because FL was 15-16 years old when the drama came out and ML was older than her.
Just like any other drama, this will only appeal to some people and some won't like it.
For me, I think the romance & chemistry was fine. I don't think you need sex scenes or kissing scenes to show a couple's affection/chemistry toward another. And I'm sure they didn't include those scenes because they knew people would feel a bit weirded out knowing the girl's real age. I was more weirded out in Goblin tbh where they had kissing scenes along with the age gap. So I can't understand why people felt there was no romance/chemistry in here.
I think the drama was engaging for most part, yes I felt like they could cut down some of the same "villain outsmarted good guys or good guys got the upper-hand now and outsmarted villain but then again villain strikes with upper-hand" episodes.
This would've been easily done in 16 episodes.
I have to say the villain was nicely developed. The flaws in this drama are plotholes. Couple of things that don't make sense and was never explained and we're left clueless making assumptions. The ending was one of them. Another one was we see people and they just randomly disappear in the show and never explained as to what happened to them. Or random characters appear and we aren't told much about them.
There's some decent action scenes and the black magic and curse aspect did attract my attention. I think they should have explained more regarding some of the things that were unanswered. 20 episodes should have been used wisely for that to clear confusion.
Overall not a bad watch, My first time watching a drama with YSY and KSR. And they didn't do a bad job. It wasn't the best drama, but it isn't the worst either. I didn't get bored at all nor did I felt anywhere I was forcing myself to watch it.