Let's get it right from the start. This movie does have faults - the plot does lose its relation to common sense some times (at least once, but in a very key moment) and it does sink a few times in to very shallow cliché such as the basic premise of the virtual world which makes this story move - translating our inner qualities into a singular personal avatar that really represent who we are. But once again I find myself watching a movie, realizing it has faults and feeling these faults don't matter one bit. I rated it 8 stars but it felt much more like 9. Because Mamoru Hosoda understands the human soul like very few do. I've seen already one of his earlier films - Mirai No Mirai where the very same deep understanding is demonstrated, I rated it 9 but I must admit this movie was much more moving than Mirai. Because the earlier movie is much more analytical and easy to relate to intellectually, while this one works on a pure emotional level. I'm rarely moved by an animated film like I was while watching it, because the characters were real - it has a lot to do with the superb Japanese voice acting, I'm not sure it'll work so well when dubbed but in Japanese it was raw and real and spoke of real issues of grief as a formative experience and about learning to stand for your beliefs against overwhelming odds and about how the smallest support from one's friends can mean the world and work wonders.
One more point that wasn't made by the previous reviewers - it's called Belle (in English) because it's using the French La Belle et la Bete as a major point of reference. It's not Beauty and the Beast in a straight forward manner but the idea of Beauty's love as a releasing power is at the core of the movie. See it and you'll see what I mean, because I won't be adding on that issue.