This one this a gem, besides episode 17, which was a bit confusing to me :D
So what you need to know beforehand. This drama has 17 episodes, but only 16 are related to the key story, while the last episode seems to tease a second season with new main characters or something like that. It is possible they only did that for could because the main character was Shinees Min-ho, but whatever. I genuinely liked that the episodes were quite short.
The story focuses more or less on three couples and switches between past and present time of their relationships. We get to witness how they get together, maybe break up and experience their lives, some trying to get back to one another. All the characters are related to each other somehow. We have three best friends, lovers, cousins, etc.
The series has a Modern Family type of vibe since it is a Mockumentary. The characters are participating in a project, where people talk about their past and ongoing relationships. The other participants can read about the stories of the others, but don't know who they are. This leads to them commenting on somebodies experiences and falling into a discussion.

The acting was AMAZING. I am usually not a massive fan of Ji Chang Wook but here he was very good. His character slightly going insane, the screaming, the mad eyes. It was hilarious to watch. Kim Ji-won really made me hate, like, love and understand her all at the same time. She was truly mesmerizing. For the other 4 roles, they choose a really great cast. At some points I wished we would even get more insides into their lives, but the amount increased as the story developed.

I really enjoyed watching the different developments of relationships and in what direction they were going. I understood why characters hesitated or made their decisions in that way. Furthermore, I also liked the cinematography and the way they included oldies music. I wanted to be a part of this cool group.

In the end there were quite some strings open or rather just opened, and I hope they will produce another season. For one couple, I did not completely understand why they chose to not be together, since they communicated about liking each other.
But overall the drama was fun, serious and full of tension at the same time. As I am writing this now, I genuinely want to rewatch it. (I completed it around February.)
You will see some new sides of Korea and many beauty shots. (a bit cringe but also cute :D)

The last episode was a bit throwing off since I did not know the content was a different one. I thought I would get answers to my questions, but no...
I don't remember them at this point, but anyway :D.