I would never recommend this drama to anyone.
It starts off brilliantly with the fascinating "life-span clock" concept, and the chemistry between the actors is good. However, the characters of the ex-girlfriend and Doha's fiancée were overdone.
I began watching it when it was still ingoing because of Lee Sung Kyung, inspired by her previous work "Weightlifting Fairy Kim Bok Jo", but it turned out to be a waste of time and a disappointment.
The ending was confusing, and there were several plot holes that needed closure and explanation.
I couldn't stop watching this drama because I hadn't yet learned how to let go of things I don't like.
All of this is my opinion!