I'm rather surprised that this drama did not have any boring bits for me, and that it was actually a solid watch. The drama focuses more on the plot and the mystery, rather than any character growth, though there is a certain complexity to some characters. I like that the drama did not delve deep into too many things, and only lightly touched issues like stalking, mental health, bullying, cheating, depression, dealing with death etc. The drama continued to keep its focus on the central mystery i.e. the fact that one by one, the people who have undergone 'reset' are dying.
I think that the biggest flaw in the drama is the fact that it does not provide any plausible explanation for the 'reset', the very backbone of the drama itself. I find it rather stupid that you can just drive down a certain route, off a cliff and magically end up exactly one year in the past with your memories of the future intact. At one point the drama showed Miss Shin ingesting a mysterious liquid before reset but that never came up again. The main villains clearly lacked motive. They just seemed to be doing bad things because they were bored.
Despite these annoyances, I did like the drama. It isn't super amazing, but it's pretty good.