As a 20 year old male I am extremely outside the target audience for this movie. Yes, this movie is for kids. In fact I'd go as far to say that this is one of the best movies for children of all time. It's a simple story. It's also an incredibly happy movie. You feel better after watching it. I can see having this movie watched over and over again by my kids when I'm a father. It's just cute and safe.
But if you consider yourself an anime fan, and you like the Miyazaki movies you've seen so far, and even though you are probably outside the target demographic, you have to see this movie! If anything just to see the movie that gave Studio Ghibli its mascot.
