Bull is a former veteran hunting dog and best friend of Ron from the Lonely Ron short stories.
He's a black and gray Kai Ken with two scars on his right eye.
He is slightly aggressive and grumpy at the times but he has a good heart.
After Ron escapes from his owners he befriends Bull and they stay together in the wild. Bull had his intestines coming out of him due to a boar attack and made him loose his trust on humans. He is being pusued by the leader of a pack of wild dogs which the leader is named Vamos along with several of his other pack members because he entered their territory.
When Vamos and the others find Bull with Ron the surround him and even though he fights valiantly he is outnumbered and becomes injured by the attack. Bull however puts his intestines in place and tells Ron to get him some water. While Ron was out, Vamos came back and almost had Bull killed. Ron returned and believed Bull died, so he went to get revenge.
Ron seeks out Vamos, and Ron fights him resulting in his exile from the territory. After the fight, Bull is revealed to have survived and his wounds heal. After that, he and Ron continue to adventure together.
See more pictures in Bull (Lonely Ron) (Photo Gallery).