Gerotora

is a "scroll toad", a rare species that closely guards whatever secret has been written on its scroll-abdomen until his contractor dies. He resides in the body of his contractor, and is known for his excellent endurance.

Gerotora guards the scroll which acts as the "key" to the Eight Trigrams Seal located on Naruto Uzumaki's stomach. The key was left to Jiraiya by Minato Namikaze upon his death, and Jiraiya in turn leaves it to Naruto when he dies. Gerotora voices his concern about this, pointing out that the key would essentially be being left upon the very "safe" it opens. He also does not think Naruto is ready to tamper with the seal. Jiraiya said that Minato gave him the key's jutsu design as a sign that Minato had intended for Naruto to complete an as-of-yet still unknown jutsu.

Hunt for Itachi arc
He first appears when Jiraiya summons him, so they could talk about Naruto's key. Jiraiya wants the scroll to go to Naruto since he thinks that he was going to die. Gerotora angrily refuses, believing that Naruto isn't ready, but had no choice.

Gerotora was one of the toads (Fukasaku, Gamabunta, and Gamakichi) to visit Konoha to bring news of Jiraiya's death.

Fourth World War arc
Gerotora is summoned by the Great Toad Sage and is told to give Naruto Uzumaki the "key" to opening and closing the Fourth Hokage's seal. He tells Naruto that with the "Key" he will be able to release the Nine-Tailed Demon Fox completely if he wanted to, by putting his hands on the square. He goes on telling Naruto that the "Key" is also the ticket to perfecting an as-of-yet unknown jutsu.

Trivia

 * In chapter 489, he is called.