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 considerably large amount of knowledge when it comes to human-toad combination jutsus and nature 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, Sakura was slowly being crushed, and Naruto 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. 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. After successfully synchronizing with them, Naruto learned that neither of them had any skill in Water Release jutsu. With Naruto's help and lessons from their father, Gamakichi teaches the basics of Water Release to Gamatatsu.

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. This enables Gamatatsu to break through the barrier, after which they return to Myōbokuzan. To their annoyance, however, Naruto keeps summoning them again, both to combat Team Guren and the Three-Tailed Giant Turtle. While fighting the latter, Gamakichi pointed out that their Water Release jutsu would be ineffective against its own water-based abilities. Naruto lamented the fact that they had no Fire Release jutsu at their disposal to evaporate the beast's water, but Gamakichi pointed out that he could perform Fire Release: Flame Bullet.

After sending Gamatatsu back briefly to Myōbokuzan to bring back a stomachful of toad oil, Naruto, Gamatatsu, and Gamakichi combined their jutsu to create the Wind Release: Toad Oil Flame Bullet. The resulting inferno 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 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 stays with 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. He is later seen with the other villagers congratulating Naruto for defeating Pain.