Karas is a difficult movie to get into. Originally it aired in Japan as a 6 Episode series (brought over here as two movies), and labeled as the 40th Anniversary Project for legendary Anime Studio Tatsunoko. I can only imagine the kind of high expectations coming from this series.
Karas is somewhat symbolized by Yin and Yang. Karas, the armored warrior who protects the city, is Yang, while the cat-themed girl Yurine is Yin. They both serve the city as an organ would serve the purposes inside a body. Another dichotomy is that the city if inhabited by two sets of people, Yokai (Japanese Spirits, or Demons) and the humans who cannot see them.
Two opposing forces clash in the movie, as the former Karas of the city, Eko, has decided to punish humans for their arrogance in forgetting the demons in the world. The city, in an attempt to defend it's self from this threat, creates a second Karas to defeat Eko. Otoha, a gang inforcer who can feel no pain, is chosen when he nearly dies. He becomes Karas and fights against Eko. Eko surrounds himself with Mikura, who are ghosts who have undergone a transformation to become machine-like.
The series is simply drowning in symbolisim and creative storytelling. That both the series' strength and it's weakness. Many people found the first movie (the first 3 episodes) to be confusing and confounding. It would have been so much more successful, if the series had been released all together, because every question you have in answered in the second film.
The story is beautiful in it's simplicity and complexity. It challenges the viewer to pay attention, and rewards viewers with a rich and deeply enchanting world.
While the plot of the movie might be hard to initially grasp, nothing falls short in the artistic beautiful and explosive imagery the movie creates. Using 3-D models alongside traditional animation - the entire film is painted with endless detail. It makes the city come alive, and thus gives you a better sense of why this dark character represent the city.
I'd highly recommend this to any Anime fan, though you'll have to be prepared to be a little confused about certain things when you first view it. Yet the wonderful thing about this movie is that, despite the challenge in understanding the story, you still want to watch it - so repeat viewings become welcome and useful.
The entire film, from it's story, characters, and creation seems to be ingrained in Yin and Yang, two sides, completely opposite from one another, functioning as one.