This was a really great movie! I recommend watching all parts at once, right after each other since the episodes are quite short. The relationship between Gitaek and Chisoo was very cute and lovely.
The story is like if you put ten different fanfiction tropes together and mashed them but it somehow works? It's fun to watch and it's still unpredictable at times. The acting... the main actors are good, the smaller ones not so much. But if you focus on Gitaek and Chisoo only + Gitaek's noona - it's well done. Music doesn't really stand out. I will definitely rewatch this with my friends because it's so good. I really recommend it and furthermore:
it has a happy ending! So don't worry about not watching if you don't like sad stories.