Really sweet, interesting entertaining, and well made – Japanese animation is the best! There’s really nothing I disliked about this movie, but it’s not perfect. I always enjoy films that deal with some form of time traveling. This one isn’t especially thoughtful in that regard – in fact, you can’t enjoy this movie if you take the time traveling concept too seriously – but it doesn’t matter.
The time traveling element is more or less used to drive the story and emphasize the themes; it’s not a discourse on the laws of time travel and it’s not trying to be. Sure, there are plot-holes, but it doesn’t matter, it’s the characters, story, and emotional ride through time that does; so, do yourself a favour: ignore the paradoxes and just enjoy the film for what it is!