There isn't much to analyze about this drama, everything happened correctly and well-done. The CGI of the parasites was just good, nothing spectacular. The performances were good though, however, I found the acting of the actors as parasites to show that they have no emotional and facial expression quite hammy.
In my view, it was a closed ending, but with a hint for possible continuation. To be honest, if there is a continuation, I will watch it; if not, that's fine too.

The drama was too short in my opinion.