This second and last movie of KOR is based on the homonym first novel of the three written by Kenji Tarada, also author of the screenplay of the movies and the series. As you can read in the synopsis, the movie tells the story of a new accidental time travel of Kyosuke.
Animation
I'll only comment the character design, since it oushines all other visual aspects. Takayuki GOTO, who worked in the animation of the series and the first movie, is the author of the character designs in Shin KOR.
For those who have watched the KOR series, how many times have you wondered how pretty Madoka could be in modern animation? With this movie you'll find it out. And I'm pretty sure you won't be dissapointed. The new designs of the three main characters are quite an improvement from the original ones, but at the same time, they remain faithful to the essence of the characters. There even are some still images (and a animated secuence when Kyousuke and Madoka met for the first time at the stairs) as remakes of some scenes of the first movie and the series, where you can appreciate better the resemblance to the old designs. Also, the way the designs change with the years is quite realistic. Perhaps the 22-year-old Kyosuke is a bit exaggerated, since it's rare to grow so much when you are in your 20s.
Hikaru is the one that change most, she has a different hair style which gives her a much more mature look. But her eyes and that mole next to them remain the same.
Madoka...If you fell in love with her in the series, she'll drive you crazy in this movie. Her green eyes, her long hair, her smile, the sweet way she looks Kyosuke..
Sound
Fortunately, the original seiyuus are in this movie too. I couldn't imagine any of the characters with a different voice.
The music is mainly supported by a special piano piece with the title "Kyosuke Nº1". It's not only special because it's quite emotive but also because of the story behind it. This song is played several times during the movie, but with different interpretations, so it doesn't become repetitive.
The ending song, Soba ni iru yo (Day Dream) by Aqua, is just ok, but I prefer the music which goes with the last secuence before the ending. Furthermore, I would have cut out the ending, cause it breaks the emotion of this last secuence, which in my opinion is the best ending that could be done not only for the movie, but for the entire KOR story.
In short, although I miss the 80s style of the series' OST and Madoka playing the saxophone, I think the music of this movie is quite good.
Story
The time travel is just a premise for the story, an excuse to show us the characters and their lifes in different times. The only purpose of the story is to serve the characters, to show how they grow up, how they lose their innocence and face a new life. This is not bad as long as you keep the interest of the spectator, and here comes the main problem of the story. At the middle of the movie, the pace becomes too slow while nothing special happens. The movie could have been shortened by serveral minutes.
I miss a lot the strong symbolism that can be found in the series and the first movie, used as a subtle mean to suggest different ideas to the audience. It is a kind of signature in KOR.
Character
The strong point of the movie. Here we have the characters from the good old triangle (which doesn't exist anymore). The movie shows these main characters in two different times in their lives. We can see an adult but yet innocent 19-year-old Madoka, as well as a more mature 22-year-old version. The same with Kyousuke, but not with Hikaru, who only appears when she's 20.
Definately the best aspect of the movie is to be able to see another step further in the relationship between Kyousuke and Madoka, as well as how Hikaru has undertaken her own way in life. At the same time, it's truly emotive to realize that their bonds haven't been broken by time.
Value
This movie is a must-see for all KOR fans, even a must-buy if you already have the series and the first movie.
As for rewatching it, I found myself wanting to do that the day after I watched it, mainly to see again the sweetest scenes, and specially, to see Madoka one more time.
If you haven't watched the series, it doesn't make sense to watch this movie. It includes a sort of summary of the series and the first movie, but it's just not the same. You have to watch them before Shin KOR.
Enjoyment
Any fan of the KOR series will enjoy quite a lot this last movie and will find in it the ending that a classic like KOR deserves. However, as I've said, the movie becomes quite slow sometimes and this could be a little exasperating more than boring.