This review is a combination of both the series and the movie.
So let me talk first about the pros and cons between the two.
Pros:
Movie:
Is short and is not full of angst and the heartache part is relatively short which is understandable since it is only an hour and 42
Series:
We get to know all the characters and their backstories. We get to love, hate, and then be okay with some of them. The story was properly expressed and we can properly root for the main lead and their second leads about their life.
Cons:
Movie:
The story overall was not properly expressed and I felt that with this kind of story, it must not be just an almost 2-hour long movie. Some characters are just there because they are "needed" to be there but are not necessarily part of the movie's overall story. Also, there are so many skips in timelines (maybe because this is a movie and they need to keep it as precise as possible, and maybe because I watched the series first). So maybe for those who are going to watch this movie and series, I would suggest to watch the movie first and then the series for a more satisfactory watch. Also, I felt that the casting for the movie did not match the characters. Like for example Miki and Koreda. Also, the acting of ML and FL (for me) is a little off. I just can't seem to sympathize with them or their characters at all.
Series:
I know it only has 10 episodes (and before I watched this, I asked if it has a happy ending because I tend to not watch if it's not), and in terms of drama - cdrama- in particular, 10 episodes is relatively short but because it has at last 3 episodes of pure heartache and slight angst (these are the episodes where I start to hate the second leads, especially the 2nd FL) that I had the urge to just skip it. and watched the good part. But as they say, no pain no glory, so I pushed through it (barely) and hated the 2nd FL and felt sorry for the 2nd ML. But I have to say, the 2nd ML has it coming. He knew that the FL was still in love with the ML but still pushed and pushed the FL to marry him. And the 2nd FL, I just can't understand her logic at all.

Do not get me wrong, I still like the movie but because I started with the series that the movie felt so rushed and add to it that I did not feel the connection of the cast with their respective characters. Take for example the ML in the early part when he was hospitalized. In the series, you can see and feel his frustration that he can't work but I did not see that in the movie. Another example is when the ML is doing the "I will let you go because I only make you unhappy" scene/speech, in the series, it was so heartbreaking that I felt what the ML is feeling as well as the FL, and I cried with them but I did not do that in the movie.
However, let me say this, the ML in the movie has a beautiful smile but then again as well as the ML in the series. He even has a beautiful crying or trying so hard not to cry face because he was so happy in Episode 10 when FLs father said "Please make her happy".

So if you are going to watch the series first, I suggest not to watch the movie at all. It will leave you hanging and feeling to watch the series all over again! hehehe

Also, I love Chako!!!hahaha..