The manga was started to build support for the movie actually, because Miyazaki was not Miyazaki back then. And the parts of the manga that even existed when the movie was made are not even close to having any sort of resolution. Hell the parts that lead to the future manga volumes are not even introduced in the movie because of this.
And all of it was made by Miyazaki.
So you basically have two independent stories using the same basic concepts by the same creator.
