Genbu

In the Land of Lightning, there is a gigantic and ancient tortoise that Kumogakure has cared for since its founding. It serves as a training ground for the Kumo ninja, and is described as a moving fortress. Its size is so great that it can host other large animals as well as other natural and man-made structures. It is considered to be the equivalent of Konoha's Forest of Death.

The tortoise's shell, the "island", has an accumulation of plant life that has grown on it. Despite being described by the Great Toad Sage as a paradise, it is anything but that to humans, with signs of death and battle everywhere and large, ferocious animals populating the island. The Falls of Truth can also be found on the island. The island is protected by a Giant Squid, which attacks anything that approaches, and a high-level barrier technique. In addition, the island can move, making it impossible to find without air reconnaissance.

A and Killer Bee trained on the island when they were younger. While there, Bee tamed and befriended all the animals on the island. He now has a vacation home there. When the Fourth Great Shinobi World War begins, the Shinobi Alliance sends Bee and Naruto Uzumaki, the only two remaining jinchūriki, to the island to be hidden from Akatsuki.

A number of Konoha ninja accompany Naruto as extra protection, including Might Guy, Aoba Yamashiro and Yamato, with Motoi serves as a guide for all of them. The official cover-story for Naruto's presense on the island is that he's "examining the island's ecology." Kisame Hoshigaki was also on the island, hiding inside the Samehada, which Bee has taken after their battle, until Naruto discovered him and forced him to escape. Motoi noted that if Kisame passes through the barrier, they will no longer be able to track him down.

Trivia

 * Due to the apes and the very obscure settings on the island, it might be a reference to Skull Island from the 1933 film King Kong. Killer Bee also affectionately calls an ape "King", a possible reference to the film's title character.