When he was a pup he was the adopted son of Saheiji. Later, some years after monkeys kidnapped him, he become a hunting dog of Ninomiya who named him "Champ". He's the leader of a hunting pack consisting of four dogs: himself, Bomb, Guilder and Jack.
He is the great-grandson of Shiro and Yamabuki, the grandson of Riki and Fuji, the son of Gin and Sakura, the middle-born brother of Yukimura and Weed and the uncle of Bellatrix, Orion, Sirius and Rigel. Together with his mate Hitomi, he is the father of Kōshirō and Unnamed Three sons.
Joe is a silver brindle (tora-ge) Akita Inu/Kishu Inu mix with blue eyes. His fur is portrayed bluish in color.
He resembles his father Gin, his younger brother Weed, and his nephew Sirius.
Joe has three scars similar to his father's on his forehead and scars on back caused by a bear.
He greatly cares about his family and son. But he harbors a grudge against their father Gin because what happened to their mother.
He even hastily attacks his brother and son for having interactions with each other.
When he believes that Weed is dead, Joe begins to cry tears blaming himself for what happened thinking it should've been him not Weed who should be drowned at the bottom of the river.
He is also a dog of his word, when he made a deal with Weed to go see his father Gin after all the bears are beaten.
The brothers and their foster father moved to Saheiji's home, before being attacked by Japanese macaques lead by Shōgun. Joe was taken away and was assumed to be dead by Yukimura and Saheiji.
Joe, in truth, survived as he was saved by a human, Ninomiya, who became his master and named him Champ. Joe became a hunting dog and, while moving in the mountains, he fell in love with a former pet dog called Hitomi. He tried to convince her to come live with him and his master, especially after she became pregnant, but she was too distrustful of humans due to her past.
Death of his Mate and Children
One day, right after Hitomi had given birth to four sons, a hybrid bear attacked them and killed the mother dog along with her puppies. Joe arrived and got scarred when he tried to attack the bear. It's revealed that the youngest of the four puppies survived after all. He was named Kōshirō "the happy fourth son", so he could live happy, not just for himself, but for his brothers.
Meeting with Weed
Later, Joe met his younger brother, Weed, and revealed that he is bitter towards their father for leaving their mother alone without assistance. Joe refused to go see Gin even though Weed wished he would and didn't want to be in any terms with his brother.
Joe found and attacked the hybrid bear who killed his mate and puppies, but was too reckless and got wounded. He was saved by Weed and he decided to tell his brother why he hated the bears so much. Joe promised to Weed that he'll go see their father, but only if he managed to kill all the hybrid bears.
Joe allies with Weed and Liger's packs and together they managed to kill the hybrid bears. When it came to the battle with the final hybrid bear Weed unleashes the Battouga which causes them both to fall into the river. Joe sees that the bear is dead and his brother is nowhere to be found assuming the worse Joe wishes that it was him instead of Weed crying tears over his brother's sudden 'demise'. As he makes the journey home he explains to Koyuki that Weed didn't survive, so he leaves his owner along with his son to pay his respects and honor his brother's last wish. As they do that Koyuki has the foolish idea of committing suicide but stops her and knows with the other that Koyuki is going to be a mother so they return to Ohu. But, to his joy Weed returns alive and well, then after that Joe forgave his father and he goes to Ōu along with his son to greet his father.
Some time later Joe becomes an uncle to Weed and Koyuki's children.
During the earthquake, Joe and Orion were separated from the pack as they got lost at the crevasse which, in turn, made them fall into the river. Joe shielded little Orion with his body when the river current carried them downstream, but he hit his head on the rocky roof and lost consciousness. Orion was separated from his uncle and survived, while Joe drowned. Just before he died, he told Orion to never give in to bullies and always fight for what he thought was right. Joe's final words were part of what made Orion strong and ready to fight for others.
- He and his brother Yukimura are the only dogs who use the attack Neck The Killing.
- According to Yoshihiro Takahashi, he killed Joe because he felt he was too similar with Weed, and so his 'role was over as a main driving force for Orion'.
- Oddly, the kanji in which his name was originally written in ("誠") is actually read as "Makoto", which means "truth" or "sincerity". This switched to the katakana for "Joe" soon after it appeared. Though it had the furigana beside when first appeard.