Gerotora

Gerotora is a toad coloured in black and orange, marked with dark patches around his eyes and mouth and a round spot just beneath his mouth. His midsection can unfurl into the scroll he carries, and when it stays tucked away the folds read like an obi wrapped about his waist.

Gerotora is a deeply doubtful sort. He scoffs at the notion that anyone, such as Madara, could linger alive from the village's founding all the way to the Fourth Hokage's era, and he never quite shares Jiraiya's confidence that Naruto could master the Nine-Tails and its power.

As a scroll toad, Gerotora possesses remarkable endurance and dwells inside his contractor's stomach, protecting whatever secret is inscribed on him; he is also able to hover in the air. The secret he keeps is the key to the Eight Trigrams Seal set on Naruto's belly. Minato Namikaze summoned him during the Nine-Tailed Demon Fox's assault on Konoha and etched the key onto his stomach for safekeeping, then passed the key to Jiraiya before dying. Roughly two years into Naruto's training under Jiraiya, Gerotora was called up again so his master could loosen a bit more of the fox's chakra as Naruto learned to draw out two tails. The toad argued hard against it, and he was proven right when the plan misfired: the Nine-Tails surged out, hurling Naruto into a four-tailed Version 2 form and taking over his body until Jiraiya sealed the chakra back down.

Later, in the story of Jiraiya's youth, the sage summoned him again to talk over the key on his abdomen, wanting it handed to Naruto in case he fell in his coming fight. Gerotora refused in anger, convinced the boy was not ready, but Jiraiya insisted that Minato had left the key's design as a sign Naruto was meant to finish an unknown technique, and the toad grudgingly relented as his summoner left. He was present when word of Jiraiya's death reached Naruto. During the buildup to the Fourth Shinobi World War, the Great Toad Sage sent Gerotora to deliver the key at last. He admitted he did not fault Naruto for hesitating, then laid out how the seal worked and warned that the Nine-Tails could break loose if Naruto's will proved weaker than the beast's. Once Naruto signed the contract, Gerotora slipped into his belly through his mouth, though it took a kick from Fukasaku to send him all the way down.