Manga is complementary to the movie. Characters are more fleshed out (apart from Akari, whose presence remains more or less nonexistent), and "Poem of sky and sea", that focuses on Kanae and now serves as coda, is completely new content. Personally i loved all versions (including light novel, which is really crappy written, or it just translates that way), but if someone didn't like the motion picture, manga won't sway their opinion.