I couldn't decide if I should give this drama a low rating or a high rating. In the end I chose high rating because I enjoyed watching this drama.
The other reviewers and commentators of this drama are absolutely correct in saying that the writer and the director really messed up a potentially an excellent/memorable drama. This drama, for me, had all the right ingredients: Love, Laugher and a naive FL who went through hardship of her life with a smile on her face.
The cadence of this drama was like any other drama but the presentation was very pleasing and was uplifting. Every night I would look forward to watching the next few episodes after a hard day at work.
In my opinion, if as a viewer, you can ignore two major flaws then this drama is absolutely beautiful with a poignant message: 1. The age of ML who is 19 but behaves like a mature 28 year old. 2. The last 10 minutes of the final episode.
Point #1 is not a big deal and as viewer one soon forgets the age difference. I could never buy that he was 19 because his emotional intelligence was very high. However, #2 is a big deal and messes up the whole drama.
Maybe the director or the producers were under pressure to give a happy ending which really made the whole ending ridiculous. It would have been better if everyone lived in the fond memory of JUN who made a huge difference in other people's lives by being caring, listening and loving person.

I am glad I watched this drama due to its light hearted approach to life played by both the FL & ML and the supporting actors. However, if you do decide to watch it, just try to ignore the two main flaws of the story line.