The Forgotten Island

Bound for the Land of Lightning, the crew loses Guy when an enormous bird carries him off toward a volcanic island. Following the trail, the group splits up. Aoba fixates on a strange girl who keeps watching them and gives chase, while Yamato and Naruto comb the terrain for their missing comrade. The pair run into a menagerie of oversized creatures before reaching the bird's nest, where Guy turns out to be unharmed and pressed into duty as a caretaker for the chicks.

Aoba's pursuit reveals the island's real purpose. The animals were raised as material for summoning contracts and for experiments aimed at producing the Ultimate Summoning Beast. Trailing the girl into the volcano, he stumbles onto a huge sleeping creature inside a deserted laboratory. His Psycho Mind Transmission tells the grim history: the beast grew too strong to control and consumed both the island's summons and the researchers before falling dormant.

The bird brings Yamato, Guy, and Naruto together with Aoba at the volcano, and the disturbance rouses the monster into a rampage. It wields genjutsu and Lightning Release, so Naruto readies Sage Mode behind a protective wooden barrier from Yamato while Guy and Aoba buy time in close combat. Guy drives the creature down into the crater, but it unfurls hidden wings and tries to climb back out.

The bird that abducted Guy dives in alongside the other summons to hold the beast down. The girl, revealed as the spirit of Honoka whom the researchers had used to bind the creature, reappears and locks it in place. Naruto lands the finishing blow with Wind Release: Rasenshuriken, flinging the beast into the molten core and ending the threat for good.

When Naruto shifts into Sage Mode here, his canine teeth lengthen in a way that echoes his Nine-Tails transformation. Among the summons rallying to keep the beast trapped, a couple of chameleons appear that closely resemble the Giant Snake-Tailed Chameleon associated with Pain. The episode belongs to the filler Paradise Life on a Boat arc.