He became an ally and commander of Hōgen.
Kamakiri was a cruel and ruthless dog, almost as bad as Hōgen.
He even killed puppies without mercy. He often laughed at the pain of others and tended to insult his opponents.
Kamakiri was very power-hungry, planning to take over the whole Japan. He believed that the strongest should rule and have permission to be as cruel as they want. He was very proud, seeing himself as superior and getting furious every time he failed or was humiliated. He had great dislike for Hōgen - probably bitter because the younger dog was the real leader of the army instead of him.
Still, Kamakiri wasn't completely bad or at least had a some sense of moral. Even he was disgusted when Hōgen used his own minion as a shield, thinking that he had went too far.
He also had a sense of honor and pride, not wanting to run away when facing the enemy and was ready to die as a male.
In the end, he was greatly humiliated and broke down physically and mentally, and his "bad deeds returned to their doer".
Ginga Densetsu Weed
Not much of Kamakiri's past is known expect that he was apparently raised in bad way and was banished from his original pack along with Stone and Shū. Yukimasa found them, lost and starving, and took them in.
Instead of showing gratitude, Kamakiri wanted power and eventually decided to take Yukimasa's place with force. He got help from Stone and others. Yukimasa's son Hiro tried to defend his father and in anger Kamakiri blinded his other eye. While Kamakiri focused on killing Yukimasa, one of his minions called Tetsu ran away with Hiro. Kamakiri later forced Tetsu's friend Pedro to kill Tetsu.
Kamakiri decides to join Hand on the way he attacks Wakayama, Rocket's home area. He kills Rikiya and steals from humans in order to get the last of the local dogs killed. Kamakiri meets Weed's pack (and grown-up Hiro). They have a short fight until the humans with guns arrive and they have to leave. Kamakiri is furious because Weed managed to give him wound and in anger kills one of his minions.
After this, Kamakiri goes to see Hōgen but is humiliated by the Great Dane. The two leaders make their closest minions fight for them in order to decide which one of the leaders gets the higher rank. Hōgen's right hand Murder S easily kills Stone, thus Kamakiri loses and becomes a minion of Hōgen and lower in rank than Murder S.
Later, Kamakiri and Hōgen move to Ōu and make Gajō their main fort. When Genba's platoon is attacked by the Ōu dogs, Kamakiri and his soldiers are ordered to help. When Genba dies and Murder S doesn't show up, Kamakiri eventually becomes Hōgen's closest minion though the two don't really seem to like each other.
Kamakiri, still greedy for power as always, wishes to take over Hōgen's army and rule the whole of Japan. His unit of 200 dogs is Hōgen's strongest, even stronger than the ones of the officers.
Kamakiri tries to catch Weed many times but he fails. While searching for Weed, he meets Hōgen's banished officer Tōbē instead and takes him back to the fortress. After finding out that he's a traitor, Kamakiri attacks Tōbē with his soldiers. The Tosa stays to fight them in hope of giving time for Takeshi and Kyōshirō to escape Hōgen's territory. Tōbē kills many of Kamakiri's soldiers until the Irish Wolfhound manages to break his skull and kill him.
Later, Kamakiri hears that Gajō is going to be blown up by humans. He stays away from the fortress with his soldiers. When the fortress blows up, he believes that Hōgen died and that now is his time to rule.
Kamakiri quickly notices the Ōu's dogs and attacks them due to their lower number. He gets into the fight with Hiro who wants to avenge his father. Hiro eventually manages to cut off his fangs and rip off his testicles, making him humiliated and unable to fight back.
Kamakiri is left bleeding on the ground. He tries to attack Hiro but he fails without his fangs. Hiro wishes he will learn to respect others and understand their pain by living with his own mauled body. He tells him he should head to South where there are rats he can catch even without fangs.
Kamakiri is then left alone, lying and screaming. The scavenger birds gather around him and eventually eat him.
Ginga Densetsu Weed: Orion
Years ago, he had a mate. He abused her which eventually made her leave and soon his sons left too. This likely happened closely after Kamakiri took over Yukimasa's pack.
"I will not let any grass grow there, where I marched!"
- Kamakiri describing the way to conquer areas Ginga Densetsu Weed volume 14
See more pictures in Kamakiri/Gallery.