Byakuren No Fang
As a puppy, Ken'ō's master was killed in a car accident and the only survivor, the son of the family, took care of Ken'ō. He trained him to become strong, but only as a working dog. Normally he didn't participate in dog fights, until the day where he and Kenichi was almost run over by Yoshimura's family.
Ken'ō enters a match with Zero, but the fight is short. Both Ken'ō's and Zero's master throw the towel in the ring and the match ends without a winner. However, he and Zero's master becomes friends and so does Ken'o and Zero.