My expectations for this were set too high by the general tone that headed my way via the Internet. It is certainly a lovely simple film for children but really it is no more than that.
It looked gorgeous and full of delightful detail (just like a beautiful picture book) but the story was featherweight (or Spillerweight if you prefer). The motivation for Haru's behaviour wasn't really explained and the characterisation of the mother was borderline ridiculous: I'm surprised she managed to survive to middle age being that useless (and why was she such an old mum? It was like watching an old Hollywood movie when all mothers were grey haired and wrinkled).
For me, the best thing about the film was that the cat turned out to be a bit of a sweetie and not a typical film cat baddie.