He was raised alongside his father as a hunting dog for a time, but often got scared by the bigger animals and failed. Kenichi and his father now use him as a hunting dog as well, with the aid of his knife, where he hunts down the animals without fear and with cold-blooded intent.
He has a white fur and wears a green collar. He has a star-shaped pattern on his forehead. He has a slashed left eye and it's unknown how he got it.
At first, Yamato viewed him as a ruthless killer and in the wild with his knife he is a skilled fighter. But in the ring he isn't very skilled as the two spend time together he comes caring of his younger brother
As a puppy, he was timid.
Shiroi Senshi Yamato
He first meets Yamato through a fox, which was Yamato's friend but Hayate's quarry. Yamato tried to help the fox escape, but failed and was impaled through the foot by the one-eyed dog.
The second time they meet, Hayate is attacking a bear, which Yamato thinks is attacking the dog, unprovoked, but later learns was just defending her cub, which Hayate then kills as well. Both enraged with each other, they fight - but Kenichi's father stops it and reveals that the two dogs are brothers.
After Kenichi and Ryo become friends and the brothers grow closer, Ryō suggests that a strong dog like Hayate should become a fighting dog. This begins his career.
Hayate invents his own special attack for the ring: the Neck Rolling - inspired by his use of the knife to behead bears in the past.
Hakugin no Teiō
Hayate and Kenichi are returning from a shop in a snow storm, when they meet Han, Kinji and their three dobermans. The dog thieves would like to capture Hayate, but Hayate drove them off using his knife.
The next day, Hayate leaves Kenichi hunting with his father, but then the same thieves attacked. The dog thieves kidnap Kenichi's father, leaving a wounded Hayate to the ground, assuming that he would die. However, Hayate survives and drags himself to Kenichi, Ryō and Yamato. Ryō calls the cops, but Kenichi wants to leave immediately to help his father, so Hayate leads the boys and Yamato to the Mountains. They found the villains in a cottage. Ryō and Yamato dribble the villains and their dogs, so Kenichi can release his father.
Yamato manages to strike one of the dobermans at a tree, but he is outnumbered by the other two. Hayate helps his half-brother by cutting off the dangerous spiky collars of the dobermans with his knife. Hayate defeats one of the dobermans using his attack called Neck Rolling, while Yamato defeats the last doberman. After this Musashi guides the police to the thieves and the thieves are locked up.
The next day, the police chief rewards Hayate, Yamato and Musashi with a honorary title called "Silver Emperor".
See more pictures in Hayate/Gallery.