So I watched the show while it was airing and only now am writing a review? Seems odd but I had to. I was unable to think about this drama without crying for a long time so I needed the time to calm down and piece my thoughts together. So here I am, finally reviewing my favourite show of all time.
Story:
This drama is incredibly well written and every thing that happens makes sense in the world of 2521. HeeDo and YiJin are our female and male leads, both having different backgrounds and ways of thinking about the world. They mirror and oppose each other perfectly. The story is that in the future, HeeDos daughter is looking back at her moms past through her diaries. We see HeeDo as she meets YiJin, as she works incredibly hard to get where she wants to go. But the drama does give us YiJin solo moments so we as the viewers know things that HeeDo does not but also are given the chance to connect with YiJin as he works to rebuild his family. I also want to clarify the age thing. HeeDo, in Korean age , is an adult when we first meet her. She is 18 Korean age so she is an adult. They don't begin to date until she is 19/20(I can't quite remember) Korean age but she was always an adult. Plus the friendships in this drama were so sweet and wholesome

Acting:
Phenomenal on all fronts, each of them did an excellent job. No complaints.

Soundtrack:
I already preordered the ost, need I say more?

Rewatchability:
For me, never. This drama tore my heart out and I can't watch it again but for you, who probably won't sob for 30 minutes after watching the final episode like I did, it is definitely rewatchable.

Overall:
Please watch this. It is so good