Let me just start by saying that what pushed me to write a review is the fact that I found a couple of reviews here who stated some very strange and unbelievable nonsense regarding the concept behind the story here as being a mystery of who will become the father!!!!! What?! I will not say haven't you been paying attention through out the show for hints or whatever, rather Haven't you watched the first episode for heaven's sake? Very early on the viewer is outright shown that the outcome of the romance that is about to unfold is unfortunately doomed, that the grown up FL's daughter's father is someone else other than the ML.
The fact that some people failed to grasp that, most propably I would guess out of sheer unwillingness to accept the fact that a KDrama can willingly choose to do that, and they kept watching with the hope that a twist will come along that will explain how the ML for some freak reason changed his name and had plastic surgery making him unrecognizable both in physical appearnce and identity to his own 14 year old daughter. Come on guys!!! If the girl was mearly reading written diaries written in codes, I would understand the mix up, but she was shown albums of old pictures by her grand-ma and she was inquiring who was the ML in the pics?! Her mom was mentioning her dad as being very much alive and working overseas! HELLO!!!!

now that I have vented out my anger at those delusional viewers who unfortunately end up giving lower ratings to the show because of their unfounded disappointment at the ending, let me very briefly state my humble review of this show.
I need not say just how much I enjoyed it, since my above rates just show, but let me state that I totally LOVED the idea of a show about falling in love AND breaking up, and not in the common fashion of heartbreak and angst, but rather the characters and their lives progressing in a way that shows them maturing by the passing of time and accumulation of experiences, and how their budding romance was a very important part of this process, how they both paved their own paths to a successful future with support from the other, and how those paths started to deviate from the other naturally. Because honestly, to me this rings more truth more than all the happily-ever-afters that we constantly get shown on TV and in movies.
Also,, let me put it out there, I would understand if people are disappointed with La la land for example, but this one is just totally different in that we knew the fact beforehand....way before the actual ending, actually I was thinking to myself while watching how I appreciated how the writers didn't play the boring game of "who's the father" that the reply series is famous for. As a viewer I find this to not be my cup of tea.

The only things I would have preferred had been done different in this show regarding writing, is how starting a certain point in the drama the ML's intial drive force to work hard ie his family got entirely pushed out of the picture, to the point than when they suddenly reappeared in the final episode, I was like yeah right....his family I totally forgot about. I would have appreciated if they were depicted just a wee little bit more in between especially when he was making life changing choices in his profession.
As for changes to the production, what was the need for a different actress to portray Na Hee Do as a grown up. Kim Tae Ri could have totally pulled of a 40-something mom thank you very much. I have nothing against the actress that played her (though tbh I was always annoyed by her voice) but what was the need to use a different actress for this character and this character only (other than the ML's younger brother which would totally wouldn't have worked with the same actor and appeared for a couple of seconds as a grown up). If Kim Tae Ri had played the older version as well, we viewers would certainly have felt more connection to the character, and the final scenes would have felt more seamless. Also, i honestly think that if KTR played both young and older versions, people would not have had such empty hopes that the ML was the father whol will show up eventually played by a different actor or something. Just guessing, cause I honestly can'twrap my head around viewers who were watching with hope of happily ever after. But still all those minor grievances did not really alter my opinion of the show as a whole.

If by some miracle, someone who hasn't yet watched the show and is checking out reviews to decide, is still reading this let me put it this way .....The story here is no mind boggling mystery with a title that is the only hint given (duh)...it just isn't! Rather, what this show is, is a coming of age story with a truely beatiful cute romance that will constantly make you swoon and blush and wish to fall in love the way they did, there is no love at first sight, no stupid initial denials, no love triangles, no needless push and pull, no acts of noble idiocy, none of these so well trodden tropes here, rather what you get are a bunch of strong and motivated characters with unique backgrounds and different upbringing settings, that bond during a critical part of their lives, whose existence in each others' lives was a driving force to push forward, grow up, persevere, excel, and become successful each in his own path. Their emotional connections transcends time and distance and even with no direct communications.
The pacing was great never felt any lags or rushed parts, and although the more we drew nearer to the final episode I was worried the last couple of episodes would not be able to wrap everything up and satisfy us as to what lead up to the current day time, I genuinely enjoyed the last episodes more than anything and thought they were the perfect closure to a perfect relationship, down to the last scene after the finale's credits. I just love how such simple scenes can speak loads and loads about people, their history. Just perfect writing period.

The acting was beyond amazing. I am growing more and more a fan of Nam Joo Hyuk, his acting here was simply put just perfect. Kim Tae Ri is also such a great actress and although I intially worried she would not be believable as a high school student younger than the ML, she proved me wrong. They were both able to portray great emotional chemistry. All the side characters were given enough balance of story development and screen time in a way that gave each of them a space to shine. The directing was wonderful, my only gripe would be how I sometimes felt the camera made people look like they had bloodshot eyes and extra red palms LOL

All in all, this was a great show, great writing with a good story pacing, awesome characters and magnificent performance, good direction and cinematography. Do not pay attention to the odd reviews here who say they were disappointed by the ending, it's a great show and with a fitting believable heartfelt ending. You will certainly enjoy each momente of this ride.