Princess Mononoke is a Japanese animation written and directed by Hayao Miyazaki. It was one of the first anime I bought and I was amazed how visually rich this animation was. It still holds true today. The forest is a truly magical place full of spirits and the spirit of the forest itself captures the imagination as it becomes the Nightwalker.
The animation is set in the late Muromachi period (14-16th Century) and follows the exploits of a young Emishi warrior Ashitaka. The village is attached by a demon and Ashitaka kills it before it gets to the village. In the process he is cursed by the corrupted demon. It turns out that the demon was once a boar god, Nago. The curse is potentially fatal. A wise woman in the village tells Ashitaka to go to the western lands that Nago came from.
The film deals with issues of environmentalism as humans come into conflict with the natural world. This is not dealt with in black and white terms but with some sensitivity.
It is also interesting that the two strongest characters in the animation are female (something of a theme with Miyazaki). Ashitaka is caught between Lady Eboshi (the human environment) and Princess Mononoke (the natural environment).