For me this drama is 8.5+
There have been so many reviews for this drama, so I won't repeat many of the comments by other reviewers.
I love dramas about the past lives and reincarnation. This drama was all about that topic. Life in general is a mystery and a knowledge of past lives tend to remove of some that mystery.

What I disliked:
Hours of drama that was pointless with the main story line such as the motor cycle accident. Hence, my low rating for this drama.

What I liked:
The message of this drama. I quote the ending of the drama:
"Is it so difficult to admit that you did something wrong? Is it so difficult to say that you are sorry? Someone waited for 8-years to make an apology. Someone even risked his life to keep his word. Life isn't only about the good old days. If you did something wrong.. admit it and correct it. It might be painful at times but you should fight it.. that is life. Atone for what you did for rest of your life so that you can make a fresh start." This is a powerful message for all of us and this planet would be in a different place with that philosophy.

In my opinion 50% of this drama is really good with a good message about life and how to live one's life.

Finally, I wish we all could remember our past lives with the commitment to live in the present. There have been many times that I can't explain my emotions and triggers, similar to the FL reaction to the guns.

Another story line i liked was about the character of Sophia who ended being a mom in 2017. Sophia sold out on her comrades because of her attachment towards her son. In the next life, as a mom, she chooses to abandon her daughter in her childhood. Hmmmm. what were her life lessons?... something to think about.

There are many story lines in this drama which has me doing some critical thinking about my own life. Therefore, this makes a really grown up drama.