From the beginning, this felt like it was going to be a disaster. When you have a book and only four episodes to make out of it, yes, you will panic but you have to at least summarise the story in a way that makes sense to the viewers.
You have to find a way to not make it seem like you crammed everything in.

It was noticeable that Gun was not a convincing character. The people around him would praise him to be super charming but I can't really see it? Gun's actor is cute and I feel like they didn't properly direct him to have those said charming/swoon-worthy traits to be seen as convincing as possible. I read as well that a different actor was supposed to play as Gun but they had to change it real quick for some reason so I guess there was an issue with timing.

The way the main leads' relationship developed? How? When? How? Why? Out of the blue, we were made to believe Bar has fallen for Gun? Was it Gun's oddly persistent way of courting Bar? Gun continuously following Bar around when there was no sign of hope that Bar was even slightly interested? Then, boom, the two lived happily ever after?

Overall, this probably would've been good if the scipt and plot was written better. Keep this in your "I have nothing else to watch so here you go" list.