Given that the original KOR movie ended the series pretty effectively, one would be forgiven for assuming that this followup would be nothing more than a wholly cynical exercise in dead-horse-beating. And it is, to an extent. The nominal premise of the film, in which Kyosuke gets displaced in time after being hit by a car, certainly feels forced. However, as it turns out, the film manages to aquit itself fairly well, and, most importantly, it doesn't compromise the source material.
It's an oddly paced piece of work, to be sure. The bulk of it works at the probably inevitable task of achieving some sort of reconciliation between Kyosuke and Madoka and Hikaru, and then, this accomplished, it suddenly veers jarringly off into 'Kyosuke really, really wants to get laid.' This first is done about as gracefully as one could expect; ie, fairly. It threatens to venture into well-trodden 'allegedly comic misunderstanding' territory at one point, but, surprisingly, it dodges this bullet, for once. Some may complain that the integrity of the events in the first movie is ruined by mitigating the quite violent breaking off of relations, but I don't really see that...it's only natural that, as time does its wound-healing thing, people should mellow out a bit, and, let's face it, Hikaru was treated pretty shabbily in the original; it seems only fair. Not that fairness is always warranted, of course, but in this case it's all good.
But then it just gets sort of weird; the material with Kyosuke wanting to have sex with Madoka feels very drawn-out and not a little pointless. Firstly, I find the idea that they didn't consummate their relationship in the two years between the first film and this one VERY hard to swallow, even if we ARE dealing with Anime Romantic Comedy Land, which is known to be inhabited by the most superhumanly restrained people in the universe. And secondly...well, so what? I suppose the creators wanted to finish off the whole enterprise with a bang (okay...poor choice of words), but it's such an inevitable formality that I had difficulty bringing myself to really care. And don't get me started on Kyosuke's impassioned, if not particularly coherent, little speech before the big moment. I found the kiss at the end of the TV series to be much more affecting, honestly.
What else to say...for unknown reasons, this film features new character designs. Less cartoony, perhaps. This doesn't bother me as much as I thought it would, but I still can't say I see the point, although the more mature-looking Hikaru is well-done, once you get over your double-take the first time you see her.
One thing that I found a bit disappointing was the lack of a number of characters from the show. Even if they weren't integral to the plot, it would've been nice to at least see them. I mean, come on, guys, it's not like we're talking great art here; a little pandering to the fans wouldn't kill you. Komatsu and Hatta make brief cameo appearances (which, let's face it, is really all one needs), but Yusaku--who I was quite curious about--is nowhere to be seen, nor are Kazuya or Akane (okay, so she was a minor character, but I still like her and wish she'd been in more than just a few OVAs), or, puzzlingly Kyoksuke's father. But the ultimate insult: no Umao and Uskiko! Come on, guys--get it together here.
I suppose you could watch and more or less understand this film without having seen the earlier material, although I have no idea why you'd want to. As for established KOR fans...well, what's the point in saying anything? Obviously, you're going to see it. And it is unlikely that you'll be particularly disappointed--it's not everything I could have hoped for, but it's not anything I would have dreaded, either. That's pretty good.