Re: Can someone tell me the relation?
It has never been confirmed, but many people think that it indeed was a reference to the Princess Mononoke movie, because of the markings and canine sidekicks.
So far, no one has asked Kishi, but I have a hunch that it is. Kishi has been known to throw in classic anime references; Like Dragonball, Kamen Rider and Doreamon.
Another, simpler, explination is because of his name, Kiba, which is Japanese for 'fang'.
It could be that the markings are use to resemble a set of fangs.