Genbu

In the Land of Lightning, gigantic tortoise that serves as a training ground for Kumogakure ninja. It is considered to be the equivalent of Konoha's Forest of Death. Despite being described by the Great Toad Sage as a paradise, it is anything but, 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.

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. Kisame Hoshigaki is 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.

In actuality though the island is an accumulation of plant life that had grown on an ancient turtle's shell and populated with animals. The ninja of Kumogakure have been taking care of it since its founding. When Kisame's intel got back to Madara and Aoba Yamashiro feared that they would be under siege by Akatsuki soon, Motoi reassured him by telling him that the island was actually a turtle that was moving.

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.