Akamaru

Akamaru (赤丸, Akamaru) is a nin-dog (忍犬, ninken) from Konohagakure's Inuzuka clan. He is Kiba Inuzuka's partner, as well as his best friend and companion.
At some point, while Kiba was still in the academy, his mother, Tsume Inuzuka, entrusted him with Akamaru. Although Akamaru almost immediately urinated on Kiba's face, much to his mother and sister's amusement, the two became close regardless.
Akamaru has been described as active and devoted.
In Part I Akamaru was a small puppy with white fur and resembles a Great Pyrenees. Akamaru's eyes are usually closed, and he has a dark brown nose, as well as dark brown patches on his ears and a dark outline around his mouth. His fur on top of his head is styled to somewhat resemble a mohawk. Whenever Akamaru ingests soldier pills his fur turns red and he becomes more feral, which is why he was named Akamaru (赤丸) "Aka" meaning "red", and "maru" being a common ending for male names in Japan.
In Part I, Kiba carried Akamaru around on top of his head or inside his jacket. In Part II however, Akamaru has grown large enough for Kiba to ride on his back, a difference Kiba claimed he failed to notice due to the amount of time they spend together; his general appearance has remained the same however.
Akamaru's heightened senses, such as smell and hearing, along with Kiba's ability to communicate with him, makes him a powerful ally for gathering and sharing information. He can 'sense' chakra with his nose, which allows him to judge an enemy's strength. In combat, Akamaru often takes Kiba's form (albeit having a much more feral appearance) using the Beast Human Clone technique, or combining with Kiba into a single entity for more devastating attacks. Akamaru also makes use of the Dynamic Marking technique- urinating on a target with great accuracy, allowing either Kiba or himself to easily track the target by scent. This is especially useful when they are fused together. Because of the sheer speed of their attacks in this form, their eyes become inadequate to follow the enemy. He has also been shown to be adept at setting traps such as explosive tags on his own.
Akamaru has not been known to talk like some other ninken, but did speak briefly at the end of a special new years episode in the anime.
Akamaru helped Kiba cheat in the first test, sitting on his head to keep an eye out for proctors and to get information from other exam takers. On their way to the tower during the second test, Kiba had the group stop to investigate Gaara's encounter with Team Shigure. Akamaru was immediately frightened by sensing the strength of Gaara's chakra, and was traumatized by seeing Gaara brutally kill all three Ame genin.
Akamaru fought alongside Kiba against Naruto Uzumaki in the exam preliminaries. He was considered a ninja tool rather than an additional combatant, and was thus permitted to fight alongside Kiba. While Akamaru gave Naruto some difficulty, especially after he transformed into a clone of Kiba, Naruto was able to use Akamaru to trick Kiba, first transforming into Akamaru and coming out of the smoke bomb to ambush him. After Kiba used the Beast Human Clone technique, Naruto turned into Kiba to prevent Kiba from attacking him, and when Kiba saw through his plan, Naruto transformed into Akamaru to make him think that he had hit Akamaru. Kiba then punched Akamaru, believing him to be Naruto.
In the finals, Akamaru was knocked out along with Kiba after Kabuto Yakushi, disguised as an ANBU member, healed Hinata Hyūga. In the anime, Akamaru attempted to warn Kiba about Kabuto, having recognized who Kabuto was. However, Kabuto used his medical ninjutsu and knocked Kiba out. What happened to Akamaru was left unknown, as Kabuto didn't come near him but he still passed out.
Akamaru can be seen with Kiba and the other villagers at the Third Hokage's funeral.
Over time, Kiba and Akamaru developed Dynamic Marking and Human Beast Combination Transformation: Double-Headed Wolf together. In the mission to retrieve Sasuke, Kiba and Akamaru remained with the group until they retrieved the container, but an explosive tag blew them and Sakon and Ukon into a canyon. Kiba and Akamaru initially struggled against the brothers, and Akamaru realized that they must use Double Wolf Fang. Kiba was hesitant, given the large amount of chakra needed, which would render them vulnerable if they missed. Akamaru bit him on the hand, and Kiba, realizing that Akamaru saw him as pathetic, decided to take the risk. The attack severely wounded Sakon and Ukon, but they blocked the last attack with a Rashōmon barrier, and Akamaru was injured protecting Kiba from their counter-attack, but managed to urinate in Sakon's eyes at the same time. When Ukon began taking over Kiba's body, he stabbed himself in the stomach in an attempt to kill Sakon to prevent himself from being taken over and harming Akamaru. Kiba attempted to escape with Akamaru, and, after Sakon and Ukon caught up with them, Kankurō arrived and killed both of them.
Kiba and Akamaru's injuries took some time to heal. Kiba, not wanting Akamaru to suffer that much again, vowed to improve himself.
Akamaru accompanied Kiba on his missions with Naruto in the fillers. In the Impostor Arc, his presence was used as Kiba's proof of being the real Kiba, as, while his impostor could imitate his face, he could not replace Akamaru.
In Naruto episode 184, Akamaru was infected with a toxin that caused him to go berserk. When he attacked some ANBU members who were training, the order was given to have him taken into custody. As Hana attempted to make a cure for Akamaru, Kiba smuggled his dog out of the village and escaped, having heard that Akamaru might need to be put to sleep, but Akamaru continued to lose control of himself. By the time Naruto and Hana caught up with Kiba, Akamaru had turned into a giant version of himself, and attacked anyone near him. Kiba hesitated in the face of the possibility that Akamaru might die, but, after Naruto and Hana's attempt to pin Akamaru down and administer the antidote failed, Kiba apologised to Akamaru while standing still as Akamaru leapt at him. Kiba was severely injured, but managed to inject Akamaru with the antidote, and noted that Akamaru had tried his best to avoid killing him.
When Naruto met Kiba while looking for team-mates, he noticed that Akamaru was much larger, especially given that Kiba was now riding on him rather than having him sit on his head. Naruto asked Kiba to join his team for a mission, and even proposed having Akamaru go with him without Kiba, but Kiba refused the suggestion.
When Team Yamato returned from the Fire Temple with a young monk named Sora, Sora quickly made it known that he didn't care what any living thing thought of him. He quickly got into a staring contest with Akamaru, to which Kiba became annoyed at. When Furido and his men attacked the Leaf Village, Akamaru demonstrated that his new size also helped considerably in battle, as he was able to take down several zombies without transforming.
When Kakashi was ordered to investigate the latest whereabouts of Orochimaru, Team Kurenai was assigned to work with him due to their tracking skills. When they managed to find Orochimaru's hideout, they triggered a trap that destroyed the base. Fortunately, Akamaru's nose was able to find a way out in time. Later, Akamaru began to have trouble concentrating due to a high-frequency sound. It was through this that the team realized that they were being spied on by bats. When the enemy ambushed them and rendered their sense of smell helpless with a smokescreen, Akamaru convinced Kiba to try their beast-like taijutsu to blow away the smoke.
Soon, the team found themselves being attacked by Guren. There, Kiba and Akamaru again worked together to fight off her attacks. After sensing their enemy's new overwhelming might, Akamaru saved Kiba by digging into the ground and hiding them in a pit.
After it was decided that the best way to find Sasuke was to find Itachi Uchiha, Akamaru and Kiba later assisted Naruto in searching for either of the Uchiha brothers, but they were unable to reach Sasuke in time and returned home.
When Pain invaded Konoha, Kiba and Akamaru joined Kiba's mother and Kuromaru in fighting the Preta Path. Later, during the aftermath of the struggle, he appeared with Kiba riding him to warn Naruto, Sakura and Kakashi that Danzō had been appointed as the Sixth Hokage and had just given the order permitting ninjas to dispose of Sasuke as a missing-nin.
After Kiba had signed up to be the village’s messenger, he and Akamaru are seen delivering packages and messages to the villagers.
When Konoha 11 has decided to eliminate Sasuke for his crimes and to prevent him from sinking any lower, Sakura decided to tell Naruto herself, with Akamaru, Kiba, Sai, and Lee accompanying her. They headed for the Land of Iron, but Sakura denied the truth from Naruto, and the group left to find Sasuke. Sakura managed to use a powerful sleeping gas bomb to knock out the others, including Akamaru. Kakashi later finds them sleeping in the middle of the path, and moved them to the side before leaving for the bridge where Sasuke and Sakura are. Akamaru wakes up from being smoke bombed by Sakura and returns to Konoha.
He later accompanies Kiba as the Konoha 11 speak about what they would do about the looming threat that Sasuke Uchiha posed to the safety of the villages and the relative peace that they had.
Along with his partner, Kiba, Akamaru is assigned to the Fifth Division of the Allied Shinobi Forces during the Fourth Shinobi World War. He and a team of shinobi are later sent to back up the Second Division. Akamaru and Kiba attack the White Zetsu Army with their Fang Passing Fang technique. The two are later seen alongside Neji, Hinata and Shino after the attacking Zetsu are wiped out seemingly exhausted. He is then seen with Kiba, as he tries to get an exhausted Neji to go to the medical compound. As Kiba lectures Neji about overusing his Byakugan, Neji responds to Akamaru instead of Kiba, confirming his bad shape. Akamaru is then seen carrying Neji on his back.
The next day, Akamaru alongside Kiba battle the transformed White Zetsu Army clones that had infiltrated their ranks. Amidst the battles, Kiba spots Hinata about to be attacked by an Iwa-nin and Akamaru moves towards Hinata to help her, only for "Hinata" to be revealed as a Zetsu. Akamaru later heads towards where the real Hinata is.