This was the last of Miyazaki's films for me to see. I have no idea what took me so long. It's visually stunning and the score is perfect.
It reminded me of studying the corruption of Smeagol in my religious philosophy class back in undergrad. Every person has the ability to turn into something dark and destructive, just as every person has the ability to turn back to the light. There is no real "enemy", just a person who you may or may not be able to reason with to work towards a common goal.
