 If you liked Hoshi wo Ou Kodomo |  ...then you might like Tenki no Ko |
I would recommend all of Makoto Shinkai's films, but I feel like Children Who Chase Lost Voices and Tenki no Ko have a similar theme. You don't mess with the nature of things, whether that be weather or death. Are you willing to sacrifice someone's life for what you want? Children Who Chase Lost Voices is about a man and a girl traveling through the Underworld to bring back his wife and her father. However, they need to exchange someone's life to bring back to dead. (One of the two characters knows this, the other doesn't.) Tenki no Ko is about a girl who can