He is Tenka's adoptive son.
He is a big pure white dog, with long thick fur. Gennai has black eyes and bushy eyebrows. He later gets two scars on his left eye, caused by Kenshin.
He's a strong, brave dog and loyal to his adoptive father Tenka for saving him. But as the time went on, he began to see how cruel his adoptive father is and decides to desert him.
He wishes to die as an Ohu Solider and fight for others defending them and their home.
But he does seem to have a one-track mind and is very stubborn, example, coming to Monsoon's home looking for a fight instead of rescuing Sirius.
Gennai does admire males who are brave and strong.
When Gennai was just a puppy, a human threw him and his siblings into the river in a sealed bag. Gennai was rescued by Tenka and his minions but it was too late for his siblings; they were all dead.
He became a close follower of Tenka. Kenshin over hears him talking to his pack about attacking, but the problem is resolved by talking. Kenshin returns to Kurohabaki Masamune, but later he is sent back out. Gennai finds him with a group of females and pups, and becomes angry and attacks Kenshin.
In the battle, Kenshin manages to rip off Gennai's left eyebrow and calls Hiroyuki to run back to Kurohabaki Masamune to get reinforcements, but Gennai catches and kills him. He later takes Kenshin to the tree and pierces him on a tree branch leaving him to die slowly (though fortunately, Kenshin turned out to be alive as he was later rescued by the Koga Dogs who then dropped him off at the long grass to meet Masamune).
Later, Gennai meets Masamune and the two get into a fight. Although Gennai has the strength, Masamune quickly subdues him with his speed and wraps his scarf around his neck before tying the other end to the top branch of a tree in an attempt to hang the sheepdog. Gennai falls to the ground, apparently dead and Masamune leaves. Gennai is revived by his comrades and he goes back to Tenka. Shortly after, he sees Blanca holding a female and her puppies hostage. He bites Blanca's head and sends to the dog crazy before attacking him again and killing the white shepherd for good.
Gennai appears running through the forest when a storm hits. He and his comrades seek shelter in an old abandoned cottage by Gennai smashing a hole through one of the walls. Inside, they are greeted by a voice who wonders if they pet dogs. Gennai explains his he doesn't trust humans and asks who the dog is. The white Akita introduces himself as Shion.
The following morning, Shion and Gennai travel down the mountain until they come across a river with a wooden bridge. Gennai notices something in the water and upon inspection, it turns out to be a dead boar caught on the posts of the bridge. The dogs haul it out of the water and begin eating. After exchanging information, Shion announces the reason he is in the area is to discover his roots, as he is in fact the grandson of one of Gin's siblings. He runs off and is followed by Gennai, who finds him confronting a bear that is guarding the Ou dogs. Gennai attacks the bear to protect Shion, but is wounded in the process. However, his injury is not severe and he is saved from death when Kenshin arrives. Shortly after, Bob and Shirozaru arrive and the dogs scare the bears away, leaving them alone with the Ou dogs trapped in the prison. After Ken is saved, Gennai heads with the others to find Monsoon and begin the attack.
Gennai arrives with the Pet Dog Squad, hearing Monsoon's and he's bears growls and he tells them to wait. But some of the dogs refuse to wait but the pyrenees refuses to stop them, seeing that he couldn't sit and do nothing he gives command of the squad to Rocket and leaves with Tsuyoshi, Kazuto and Minoru to provide backup. During the fight Gennai hears that Monsoon is making a big fuss about pet dogs and wonders why. Unsai explains that pet dogs are usually with human hunters that possess powerful weapons.
He got the sickle from Izo and tell him that he got serious injuries and think he can win with his spirit. He ask him that does he want to die with no shame as Ouu Soldier. Gennai tells Izo that he have wanted, he has the sickle, he can die as member of Ouu army. Izo tell Gennai to give sickle back but he tells Izo that he maybe giving up his own life. Gennai trying protect Izo and others, it's a male's biggest wish. Orion and Andy tell Gennai that he can't treat them like kids forever. But he tells them don't rush in without plan and that's why he called them brats. Orion tells him to let him have sickle and Gennai tells him to shut up and he's going to take Monsoon out. Gennai look at Monsoon and think that will make him as Ohu Legend and whether or not, he will beome one depends on.
Gennai tell every of dogs to watch, this wasn't originally his fate and he will dedicate his life for others. He will protect their canines paradise to the death. He tells Orion if he can give his life for him all, then he'll be satisfied. Gennai charge at Monsoon and other dogs tells him that attacks from the front is impossible. Monsoon aims attack to Gennai and but he passes him on legs. Gennai slipped under Monsoon's legs with vigor and without hesitation. He made good use of his body weight and thrust the sharp sickle into Monsoon's left leg. Gennai slipped in with the blade and he stayed where he was. He slashed at Monsoon's legs with all his might. Monsoon fall to the ground and Gennai was pinned and crushed in an instant, he kept on resisting until the end. Gennai had to let go of sickle and barely able to escape after being flattened, he tried hard crawling from underneath Monsoon's belly and Monsoon is about strike his claw to him, but Unsai bites his injured paws. He tell everyone that he's sorry and the sickle, the lifeline and he dropped it. Gennai fell unconscious.
Orion tell Gennai to heads up from Monsoon. Gennai rolls over from Monsoon's legs. Gennai calls Unsai after he got slash by Monsoon. After Monsoon is gone he hears Orion say to Sirius to forget the new plan blaming him for everything that happened. Gennai sees Sirius and Shion run off after Monsoon and he says he will go with them, but Sirius says they are going to talk not to fight. As he sees the two leave he tells them they can't do what they want and ask Orion if he's going to let his brother go like this.
After everyone has fallen asleep Gennai and his subordinate Tsuyoshi left to find Monson until they are met by Akakama saying that he came to face the bear even if it means dying. He tells the dog if wants to become a male he has to use his head and he also asked the Irish Wolfhound what's he doing here all Akakama says is that he came to find Sirius. Then, he asked him to be their guide since they are getting older they are met upon Kurokama and the others including Rocket and Rigel he welcomes them by Rocket tells them by Gin's orders they are suppose to go back.
He hears Rocket and Akakama bicker until it ends with the irish wolfhound deserting the army agreeing that Sirius should matter too and continues looking for the young akita and Monsoon. Then, along the way he teases Rocket about not being the fastest in the army but he collapses Gennai says this is no time to rest but Rigel quickly defends Rocket. Then, Gennai snaps about how disorderly the others are being and asks who's going to be the leader but no one responds he takes over and continues on their way while Rigel looks after Rocket.
When they make it to Monsoon's territory Gennai notices the forest watchmen by quickly ignores them. He quickly discovers the place is littered with Sirius's and Monsoon's scent and then he follows Akakama to Monsoon and attacks the bear with others following him. Finally, seeing Monsoon Gennai attacks him as the others distract Monsoon Akakama calls for Sirius, seeing that the akita is alright Akakama tells Gennai get off Monsoon and run but he refuses saying he came to kill Monsoon. During the midst, of the scuffle the bear roles on to his back but the pyrenees survives. Sirius manages to break up the fight but the akita says that Gennai is ruining the peace negotiations and he doesn't get the bear at all. But Gennai what is there to get believing that no one will live in peace until the bear is dead. When he sees Monsoon coming towards him Gennai prepares to fight.
Gennai is sent flying by Monsoon but lands on the ground Sirius tries to stop him the pyreness only tells Sirius we're nothing but to him with Monsoon's claws coming down Gennai pushes Sirius out of the way. After that Monsoon puts his paw on top of Sirius knocking him out and with that he further explains his point and goes to check on Sirius and sees Akakama hastily attack Monsoon. After that he calls Akakama a male among males with great honor and when Akakama tells everyone to go after Monsoon he calms him down by saying they have a lot of time. Then, after Akakama falls asleep Gennai and the others notice a helicopter and began to assume the humans spotted Monsoon and is still in shock that Sirius wants to stay.
Gennai hears from Sirius that his purpose was to talk not to fight. With Shion still following him Rigel watches Sirius leave wanting to have a chance. Gennai attacks 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. Seeing that Sirius wants to continue he makes another move on the akita but is blocked by Rocket and giving into his anger he told Sirius to leave. Hearing Rigel's realization that only the humans could bring Monsoon down seeing that their power wasn't enough with Akakama agreeing. He also understood that the humans don't know anything about Monsoon yet; Gennai and the others begin to hear the watchmen's dogs owner's whistle and takes the fallen hunting dog back to their owners.
After Gennai leaves Bell with an important mission, they track a helicopter hoping to lead the humans to Monsoon, until night fall and they begin to rest. They hear a scream and the others begin to suspect it was Sirius until the pyrenees calms them down. When Rigel and the others come back he sees that they were unable to convince him. He sees Sirius and Shion return to the group with the bear cub surprised that the cub is still with them, hears Rigel get asked by Sirius to take Chibi back to Ohu with them.
And after Gennai's bad choice of words Rigel blocks Sirius from attacking him. Surprised that Chibi started to speak dog language and hearing that Sirius has big hopes for the young cub still feeling skeptical about this he asks for Rocket and Rigel's opinion about this. Once Rigel agrees on taking Chibi to their home with Rocket escorting them he tells them to go and that he's not going anywhere. Sometime later, Gennai approaches Monsoon head on as apart of his plan. Supporting what Sirius said he quickly dodges the bears claws and briefly hides but coming out of his hiding place the pyreness attacks the bear. Urging Sirius and Shion to attack him once they do playing along Gennai says they have double-crossed them but Sirius is told by Gennai that he and Zion should run but he tells Gennai to run instead. Getting the idea Sirius and Zion get chased by Gennai until Monsoon intercepts them.
He gets attacked by Monsoon along with the Kamakiri brothers, after Monsoon shortly leaves he gets checked on by Sirius and Shion relieved that he's alright and takes his leave. Still keeping an in eye on the youngsters but was annoyed that he wasn't making any progress Gennai though after Monsoon is defeated he would claim this place as his territory upon seeing the trio again they were shocked with what they saw the trio getting along. Then, he was alert by Kurokama of Sirius' location and surprised to see him and Shion swimming with Monsoon and speaking bear.
Believing Sirius was in danger again he and the Kamakiri brothers come rushing but Sirius was enraged and Gennai was sooned attacked by the pup. He tried to throw Sirius saying he's risking his life for the wrong guy but got thrown instead is reminded that Sirius is trying to gain Monsoon's trust Gennai says Sirius will die by that bear before that happens. Seeing Sirius being protected by the bear Gennai sees this as hopeless and commends the brothers for stopping him. Leaving for good he tells Sirius that once everyone is healed they'll attack for sure and Monsoon will die, and when Sirius says his father will make Orion understand but scoffs it off knowing Weed won't be in command forever and his brother might be the leader someday. Also knowing Orion will be looking for revenge leading to all out war but when Sirius wants him to tell his brother to think things through the pyreness snaps.
Invoking an angry reaction from Monsoon and is tossed by the bear, Gennai told Sirius not to go near him believing that Sirius enjoys watching them get killed and sold his soul to the bear. But is informed that Sirius sell his soul to anyone having enough Gennai tells the pup he can live his life his way. Also reminds Sirius that he betrayed his pack and family just to stick up for Monsoon and couldn't understand why he was so good natured but Sirius he'll understand someday. Watching the three disappear Gennai puts his faith in Orion preparing for battle returning to Futago Pass.
- It's presumed that Gennai is a Great Pyrenees, but it's not officially confirmed.