Yamabiko is a gray-brown (sometimes portrayed black or gray) Kai Ken mix with blue eyes. He has a long, mask-like scar across his eyes and a smaller scar on his forehead.
He is kind-hearted, brave, loyal to his friends and a good fighter for his age.
Yamabiko is good friends with Orion. Despite his brother's hatred, Yamabiko still loves his older brother.
He deeply cares for Orion forbidding him not to follow them understanding that he has a more important has temporary leader of the army.
Yamabiko was born in the summer as the youngest son of Terumune Kurohabaki, who declared him the heir of the Kurohabaki Clan instead of Masamune Kurohabaki, the elder brother. The decision made Masamune bitter and he wanted to kill both Yamabiko and Terumune in order to become the leader.
Terumune send Yamabiko away to Shikoku with his guardian Kojūrō and Amon, being afraid that Masamune might harm his little brother. After this, Terumune was vanquished and banished by Masamune. Yamabiko, Kojūrō and Amon almost return back to the Clan due to Masamune's lie, but Kihē warns them about Masamune's trap. Yamabiko is then attacked by Masamune's assassins (Shikkoku, Gekka and Kurogane), but he is rescued by Orion and the puppies quickly become friends.
Yamabiko returns to Shikoku and fights Kamakiri's sons army which attacks his territory. Orion's army comes to help Yamabiko's one and Yamabiko later joins Orion's pack after hearing about his father's death.
When he sees his brother commit suicide after Masamune realizes his plans for conquest were put an end. Yamabiko told him that he was a fool and that their were other ways of dying on his own accord. So Yamabiko used his scarf to wrap Masamune and have this spot used as his burial ground. After Masamune's death, the Kai Ken finds Kojirō's body and begins to over him for what did for the young pup. As he and his friends bury him, they hear someone lurking nearby and the Kai Ken pup tells them to come and sees Kōsetsu. Then Yamabiko tells him about how it's the Ōu Army's mission to make the world more peaceful for all dogs. He explains that Masamune died on his accord, he says that he will not live by feelings and will give Kōsetsu a choice on what to do. With Orion's help he easily beats Kōsetsu and watches Gennai grab him by the neck and throw him down and chews him out for killing him but he sees that he's alright. Begins to tell Kōsetsu, that his brother was wrong about their purpose and gives them a new one, he says that the Ōu Army doesn't like to fight. Yamabiko decides to return back to Shikoku.
Yamabiko arrives in the Akame Mountains with some of his followers to greet Orion after six months. After a short reunion, Akame arrives, bloodied and exhausted to tell them that the son of Akakabuto, Monsoon, has attacked Ōu and everyone is in grave danger. Yamabiko agrees to help out and tells Orion to gather forces whilst he returns home to gather his pack along with more reinforcements.
Returning home, Yamabiko gathers his pack as promised and makes his way to Ōu, meeting up with Akame after he has recovered. Soon, the large group meets up with Andy who takes them to Orion and Bon. Their reunion is short lived when they hear the sounds of fighting coming from the nearby forest.
Yamabiko's group and Sasuke curse the bad weather, with Yamabiko saying a pet dog like Sasuke isn't used to getting so wet. Sasuke jokes he likes being wild and the group hear that Orion has returned.
Sometime later, a flood causes a wounded Ken to be washed into a river and the Ōu Army go to the location to find and save him. They each keep a watchful eye on the raging river, as Kawasemi dives in to find him.
Ken is saved and cared for by the army. Yamabiko heads off to aid Orion in the fight against Monsoon and orders his pack to attack the giant bear after he injures Akame and loses an eye and finger to the ninja dog. Monsoon whips his arm backwards, swatting Yamabiko into the trees, causing him to lose consciousness.
Yamabiko regain consciousness in the tree and hit Monsoon's red hair. Orion tell him to get out of woods. As Yamabiko avoids the Battōga, he sees that Orion's attack didn't work and he falls to the ground as passes out. So he ask Sirius to take Orion and run but when Sirius believes he can still reason with Monsoon, the Kai Ken takes it upon myself to get the red Akita to safety.
While trying to flee with Orion he sees Monsoon heading straight for Sirius. He sees that Sirius is spared from Monsoon's claws by the arrival of Daisuke and his mentor and sees the enemies flee with his injured comrades in the care of humans Yamabiko leaves with Akame and the others to find Monsoon.
Then, he comes across Kurotora's group to ask them where Monsoon went and tells them that Monsoon was scared off the arrival of humans. After leaving the woods he finds Sirius and his group, he along with the others continue to hear Sirius and Orion arguing what to do about Monsoon. Even though, he understands how Sirius feels he already knows his way of thinking won't work against these enemies. He sees both brother lose their tempers and break into a fight until it was stopped by Andy.
He continues to watch the arguments between the brothers Yamabiko tries to have them draw attention to their enemies. Watches in shock as Orion throws the sickle in anger as it hits Sirius on the head, then he hears the rest of the Ōu Army coming along with humans. Then, he sees Sirius run to the bears hoping to talk when he hears for Shion to come up he agrees with Orion for him not to go. After the bears are defeated he goes with Orion, Bon and Andy to see that Sirius is alright.
Yamabiko greets Daisuke with the others, says that Monsoon used his kin as bait and he'll attack again when the humans leave and his wounds are healed. Then, the Kai ken hears his allies cry out in victory until it's stopped by Orion wondering why the red Akita is so bent out of shape then his attention is turned to Sirius saying that this fight has to stop but hears that Orion disagrees. As the argument between the brothers continues Yamabiko watches as Andy intervenes, then after a discussion between Akame and Orion the white kishu tells Yamabiko and Andy to come here and give Orion support from now on.
Yamabiko and the others gather around Akame to see if he is okay the kishu regains consciousness and he sees Akame whispering something into Sirius's ear wondering what it was. then Akame passes out again. Thanks to Daisuke and Hidetoshi he is quickly revived and he sees Daisuke carry him away after the Kishu gives command of the army to Kyōshirō and he gives his first decree that no more fights will come between them.
Some time later Yamabiko watches from a nearby hillside with his comrades as Daisuke and the people of the village bury their fallen allies and pays their respects.
Seeing Kyōshirō's treatment of their new comrade he sees that Bob isn't going to live long. Then, he sees lord Gin alive and well and the Akita informs them about what happened to Hiro, Lydia and the others as soon as night came they all fell asleep.
Then, he wakes to see Orion, Bon and Andy needing to talk and follows them; seeing that Akakama and his brother have gone after Sirius. Yamabiko believes it was because of the vow Akakama made to Sirius and tells Orion that the three are leaving to get them. Orion wanted to go with them too but Yamabiko tells him not to be a spoiled brat understanding that the red akita has a more important role.
Yamabiko and the others manage to catch up to the Kamakiri brothers saying that they couldn't leave retrieving Sirius up to them. Seeing that they ran a great distance they all decide to take a rest deciding that the first one to get up wakes the others up but when they all wake up they discover that Akakama is gone but quickly find him with Gennai and hears Rigel and Rocket close behind.
The Borzoi tells them that Gin wants them back and hears the two them argue up to the point where Akakama abandons the army for Sirius's sake and continues to follow him with the others following close behind.
He and the others keep going until Rocket collapses; seeing the army disorganization Gennai asked for anyone of them to step up as a leader but when they don't the pyrenees takes over and continues to look for Monsoon and Sirius. As the continue their search they come across two people but quickly ignore them as the others distract Monsoon Akakamakiri calls for Sirius, seeing that the Akita is alright. He hears Sirius argue with Gennai saying that he's ruining the peace negotiations and sees Monsoon heading for Gennai.
After that is relieved to that Akakamakiri is alright. Then, after Akakamakiri falls asleep Yamabiko and the others notice a helicopter and began to assume the humans spotted Monsoon and is still in shock that Sirius wants to stay.
Yamabiko hears from Sirius that his purpose was to talk not to fight. With Shion still following him he watches Sirius leave wanting to have a chance. Then, sees Gennai attack Sirius in a fit of rage for his attitude, then they all hear a cry help only to discover that it's one of the watchmen's dogs with his front paws cut off. Hearing Rigel's realization that only the humans could bring Monsoon down seeing that their power wasn't enough he started to think that Rigel should go with his brother but Rigel didn't mean it like that with Akakamakiri agreeing. He also understood that the humans don't know anything about Monsoon yet; he and the others begin to hear the watchmen's dogs owner's whistle and takes the fallen hunting dog back to their owners.
Then, after escorting Paulie back to Bell, Yamabiko leaves with Gennai to find Monsoon during the search. They see a helicopter above, and tries to lead the humans to Monsoon. They all continue in their search till nightfall, when they smell that Monsoon's scent is everywhere. During their rest, Andy and the other hear a scream, but Gennai calms them down by telling them it wasn't Sirius.
When Yamabiko sees that Rigel and the others return to Gennai's group he sees that they were unable to convince him. He hears Gennai trying to convince Rocket to return to Ōu but he didn't want to leave empty handed the pyrenees agrees with Rocket's decesion. He tells Gennai that he is prepared for the worst if Monsoon comes. He sees Sirius and Shion return to the group with the bear cub and is shocked. After Sirius explains everything and surprisingly hears that Chibi started to speak dog language and that Sirius has big hopes for the young cub. He hears Rigel agree on taking Chibi to their home with Rocket and sees them return to Ōu.
- Yamabiko's name literally means "mountain boy." In a Japanese tale, there is a spirit that was known to live in the mountains and echo back any words and sound it heard, creating the phenomenon we know today. Some depictions show it as some sort of canine.
- Some fans believe that his and Masamune's mother could be either an Akita or an American Akita.