It's okay. It's weaker than the anime TV series, obviously, but I quite liked it. If nothing else, it gives us twice as much of Io Sakisaka's story from the original manga. Watching this straight after the anime was a mildly gob-smacking experience for me, incidentally, for how much faster it galloped through the story I knew and how much further it went beyond it.
(Quick run-down of that story... a girl (Futaba Yoshioka) has a complicated relationship with a boy (Kou Mabuchi). Three years ago, they liked each other. Now, Kou is an almost surly loner and Futaba is deliberately damaging her image for the sake of having friends.)
For me, the best thing about this film is Tsubasa Honda in the main role of Futaba. She's not perfect, but I can forgive a few unconvincing moments given how good she is otherwise. She's not just saying her lines. She's inhabiting them. She's putting energy and detailed thought into everything her character says and does. What's more, she can project this for an audience. She has charm and freshness. She surprised me and made me laugh. She feels a bit different from the anime/manga Futaba, but that doesn't matter because she's making the role her own. She's an intelligent, hugely entertaining actress and I'd be interested in seeing where she takes her career from here. Apparently she got her break in the entertainment industry in mid-2006, when she was scouted by seven different people on the same day.
The rest of the cast is fine. Masahiro Higashide does the job as Kou. The other characters' screen time has been cut right back, but Ryo Yoshizawa is putting so much into his performance as Kominato that he's memorable and funny anyway. (Is he overacting? Maybe, but in a good way.) Yua Shinkawa manages not to disappear despite having very, very little to do. Izumi Fujimoto as Yuuri makes the least impact, but in fairness (a) the character she's playing is a bit of a shrinking violet, and (b) her role's been cut back so much that it's actually damaging the story. Her confession to Kou is reported, not seen, and the "love him or not" plot developments with her and Futaba don't get enough weight to justify their existence. A big chunk of story has being boiled down to a couple of minutes. It doesn't work. Apart from anything else, that should have been a big character-defining moment for Futaba.
I think it's time pressures. The film's trying to get through twice as much plot as the TV series in forty per cent of its running time. Understandably they're focusing on the Futaba-Kou relationship and anything that directly affects that, but I think Futaba's relationship with her friends is a fundamental part of what Io Sakisaka's saying with the series. The group growing together is something I missed (e.g. the leadership training conference).
The cast's heights are slightly distracting. Masahiro Higashide is 189 cm tall and looks about nine inches taller than all his co-stars. (Well, except for the actor playing his brother.) He's also comfortably over than a foot taller than the munchkin they've cast as Yui Narumi (not in the anime). I'm wondering if there might not be an element of deliberate visual metaphor in this, given what Yui represents in his life, the story's overall theme of growth during one's teenage years and the fact that Kou three years ago was short. It's mentioned in dialogue. Since then he must have grown like a bamboo grove.
This director specialises in adaptations, incidentally. Not counting his TV and music videos, he's made eight feature films so far and they're based on (in order) a manga, a manga, a manga, a novel, a manga, a manga, a manga that was based on a novel and a manga.
This film topped the Japanese box office on its release weekend, for what it's worth. (The Hobbit: The Battle of the Five Armies made more money, but sold fewer tickets.) It's nice. It's funny. It's not perfect (more Yuuri! more friends!), but it's a pleasant romance. You'd expect something far worse than this from a live-action film trying to cover twice as much story as a TV series.