I felt that the story was too complex to be crammed into 15 very short episodes.
It wasn't conclusive, wandered and unless there will be a S2, the ending was awful.
In the early eps some cast members were quite stiff in their acting, but by the end, all seemed to have relaxed in to their roles and worked well together.
Character Su Jeong irritated the pants off me!
Definitely needed either a simpler story or longer episodes; disappointing but not absolutely dreadful.
Rewatch as a filler or for something nice to look at.