Gamakichi

is one of Gamabunta's children. He was first summoned by Naruto Uzumaki because Naruto couldn't focus his chakra during the beginning of the battle with Gaara. However, he is intelligent enough to be aware of the situation around him and realize when it's time to flee.

Personality
He is rather funny, and has the mannerisms of a smart-alec. He is also often very condescending and joking 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. When he is summoned he tends to greet people by saying: "Yo." By Part II Gamakichi has not just grown big in size but in maturity as well. Gamakichi seems to have a considerable large amount of knowledge when it come to Human-Toad combination jutsu's and Nature energy. Also he seems to be on better terms with his brother, Gamatatsu, as seen when he no longer calls him an idiot.

Part I
During the fight with the transformed Gaara, Naruto was slowly being pinned down, and decided it was time to summon Gamabunta. However, due to poor chakra control, he could only muster enough chakra to summon Gamakichi. Though irritated, Naruto kept Gamakichi safe from Gaara's attacks. When Naruto finally managed to summon Gamabunta, Gamakichi convinces his father to help in the fight, saying that Naruto needs help saving his "girlfriend." He is 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 does not have his Part II debut until much later in the manga, Gamakichi appears sooner in the anime adaptation. Noticeably, Gamakichi is not yet as big as he will be in his manga Part II debut, by which time he will be big enough for Naruto to stand on his head, (here in his anime Part II debut, Gamakichi is easily big enough for Naruto to stand on his back.)

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

Gamakichi then begins training Gamatatsu in water-chakra with what appears to be lessons from their father. After Gamakichi appears to get the basics down, they begin trying to get the combination jutsu completed for Naruto's next mission by having Naruto wait in Gamatatsu's mouth. Later, when Team Yamato find it impossible to break through Guren's crystal barrier via conventional means, Naruto summons Gamakichi and Gamatatsu to help. Gamakichi keeps Gamatatsu focused by warning him 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 brother's return home.

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

After being called back yet again by Naruto when the Three-Tailed Giant Turtle starts to rampage, Gamakichi is 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 explains to Naruto that to overcome water they would have to have the Earth Release style.

Naruto, knowing only Wind Release laments that they have no Fire Release techniques before pausing. When Gamakichi asked what he was going to say, Naruto commented that he had thought to make a Fire Release stronger with his wind chakra, but while wind could make fire stronger, the fire would still be weak against the Three-Tails water attack. Gamakichi reveals that he himself is able to use Fire Release techniques, (and 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 that could overcome the water and evaporate it.

After sending Gamatatsu back briefly to Myobokuzan to bring back a stomachful of Toad Oil, using the same timing for the Wind Release: Toad Gun technique; Naruto, Gamatatsu, and Gamakichi set up for their first improvised three-way collaboration jutsu, the Wind Release: Toad Oil Flame Bullet technique:

Knowing that the Three-Tail's only weak-point is it's eye, Naruto and Gamatatsu implement their ad-libbed Wind Release: Toad Oil Bullet technique, (a Wind-empowered Toad Oil Bullet,) against the Three-tail's own water gun. During this, Gamakichi steps up and delivers his Fire Release: Flame Bullet technique, which together with the wind chakra and oil, ignites into an inferno that drives through the Three-Tail's water attack and has the demon Turtle fleeing under the lakes surface. Once the Three-Tails was overcome, Gamatkichi and Gamatatsu go back home.

Invasion of Pain arc
Gamakichi makes his Part II debut in the manga when Naruto is informed of Jiraiya's death. He and his brother appear again during Naruto's senjutsu training, watching as he trains under Fukasaku. He is summoned again during Pain's attack on Konoha, where Naruto instructs him to get Tsunade to safety. He is later seen alongside Sakura and Kō, satisfied at the fact Naruto seems to be defeating Pain despite Naruto being in his six-tailed transformation. He chuckles at this, which causes Sakura to quickly reprimand him.