Gamakichi

is one of Gamabunta's children. He was first summoned by Naruto Uzumaki after Naruto proved unable to focus his chakra during the beginning of his battle with Gaara. However, he is intelligent enough to be aware of the situation around him, and to realize when it is time to flee.

Personality
He is rather funny, and has the mannerisms of a smart-alec. He is also often very condescending as well as light-hearted in most situations, preferring the levity of talk to the seriousness of battle. He seems to favor Naruto because he saved him from Gaara's One-Tailed Shukaku form. After he is summoned he tends to greet people by saying, "Yo." By Part II, Gamakichi has not just grown in size but in maturity as well. Gamakichi seems to have a considerable large amount of knowledge when it comes to human-toad combination jutsus and mature energy. Also, he seems to be on better terms with his brother, Gamatatsu, as shown by him no longer calling him an idiot.

Part I
During the fight with the transformed Gaara, Naruto was slowly being crushed, and decided it was time to summon Gamabunta. However, due to poor chakra control, he could only muster enough chakra to summon Gamakichi. Despite being irritated, Naruto kept Gamakichi safe from Gaara's attacks. When Naruto finally managed to summon Gamabunta, Gamakichi convinced his father to help in the fight, saying that Naruto needed help saving his "girlfriend". He was later accidentally summoned by Jiraiya during his fight with Orochimaru. In the anime, Jiraiya summoned him again to check for traps at the entrance of Orochimaru's hideout.

Three-Tails Arrival arc
Although he did not have his Part II debut until much later in the manga, Gamakichi appeared sooner in the anime adaptation. Noticeably, Gamakichi was not yet as big as he would be in his manga debut, by which time he would be big enough for Naruto to stand on his head, (here in his anime debut, Gamakichi was easily big enough for Naruto to stand on his back).

When Naruto proved incapable of synchronizing with Gamariki to learn collaboration jutsu, Naruto decided to summon Gamakichi and Gamatatsu, as he had worked well with them before. Naruto was also amazed at how much they had both grown, as they were now bigger than him. Initially, Naruto was as annoyed with their training method as Gamariki's, but, after Gamakichi explained what true synchronizing was about, Naruto agreed to try it again. Now that Naruto had mastered being able to synchronize with Gamatatsu, he then learned that neither Gamakichi or Gamatatsu had any skill in Water Release jutsu.

Gamakichi then began training Gamatatsu in water chakra with what appeared to be lessons from their father. After Gamakichi appeared to understand the basics, they began trying to get the combination jutsu completed for Naruto's next mission by having Naruto wait in Gamatatsu's mouth. Later, when Team Yamato found it impossible to break through Guren's crystal barrier via conventional means, Naruto summoned Gamakichi and Gamatatsu to help. Gamakichi kept Gamatatsu focused by warning him that he wouldn't get any snacks if he didn't focus on the task at hand. After a brief incursion against the Crystal Release user, the brothers returned home.

However, much to the latter's annoyance, Naruto soon called Gamakichi, along with Gamatatsu, back to help him cross a lake in pursuit of Team Guren. Upon arriving at their destination, Gamakichi was horrified to see none other than the legendary Three-Tailed Giant Turtle. He then appeared again along with Gamatatsu to battle against Guren to defend the sealing team that consisted of Shizune, Sakura Haruno, Ino Yamanaka, and Hinata Hyuga. Upon the Three-Tails breaking free from the seal due to Guren's interference, Gamakichi returned home with Gamatatsu yet again.

After being called back yet again by Naruto after the Three-Tailed Giant Turtle had begun to rampage, Gamakichi was the first to point out that their Wind Release: Toad Gun technique, being essentially a Water Release technique, would prove ineffective against a water monster such as the Three-Tailed Giant Turtle. He further explained to Naruto that, to overcome water, they would have to use the Earth Release style.

Naruto, knowing only Wind Release techniques, lamented that they had no Fire Release techniques before pausing. When Gamakichi asked what he was thinking about, Naruto commented that he had thought to make a Fire Release technique stronger with his wind chakra, but, while wind could make fire stronger, the fire would still be weak against the Three-Tails' water attacks. Gamakichi revealed that he himself was able to use Fire Release techniques (and that he hadn't brought it up before because no-one had asked him), and that, working together, the three of them could conjure up a Fire Release technique that could overcome the water and evaporate it.

After sending Gamatatsu back briefly to Myōbokuzan to bring back a stomachful of toad oil (using the same timing as they had for the Wind Release: Toad Gun technique), Naruto, Gamatatsu, and Gamakichi prepared to use their first improvised three-way collaboration jutsu, the Wind Release: Toad Oil Flame Bullet technique.

Knowing that the Three-Tails' only weak point was its left eye, Naruto and Gamatatsu implemented their improvised Wind Release: Toad Oil Bullet technique (a wind-empowered Toad Oil Bullet) against the Three-Tails' own blast of water. During this, Gamakichi delivered his Fire Release: Flame Bullet technique, which, together with the wind chakra and oil, ignited into an inferno that drove through the Three-Tails' water attack and had the turtle demon fleeing under the lake's surface. Once the Three-Tails had been overcome, Gamakichi and Gamatatsu went back home.

Invasion of Pain arc
Gamakichi made his Part II debut in the manga when Naruto was informed of Jiraiya's death. He and his brother appeared again during Naruto's senjutsu training, watching as he trained under Fukasaku. He was summoned again during Pain's attack on Konoha, where Naruto instructed him to get Tsunade to safety. He was later seen alongside Sakura and Kō, satisfied at the fact that Naruto seemed to be defeating Pain, despite Naruto being in his six-tailed transformation. He chuckled at this, which caused Sakura to quickly reprimand him.