A Hole in the Heart: The Other Jinchūriki

is episode 318 of the Naruto: Shippūden anime.

Summary
Gyūki notifies B who had stopped for yet another bathroom break that Naruto was far ahead of them, to the beast's exasperation Motoi catches up to B and informed them that he had been sent to assist them. As they proceed towards the battlefield, a small faction of the White Zetsu Army nearby plotted an ambush on the duo. Kabuto Yakushi who had also located B decided to enable another one of his special war potentials in order to capture Killer B. As the coffin emerges from underground — comically uncovering the White Zetsu in the process — the contents of the coffin is revealed to be Fukai, the previous jinchūriki of the Eight-Tails. As the two parties converse, Fukai advises them that he was not in control of his body and that they needed to escape but B notes that without Gyūki, he did not pose as much a threat as he would have. Fukai, however, enters Version 2, shocking B and Motoi. It is then revealed that it was Orochimaru's experiments and actions which brought about Fukai's death and Gyūki's rampage some thirty years prior. As the two men fight in their respective Version 2 states, it is revealed that Orochimaru had infiltrated Kumogakure, drugged Fukai, and extracted Gyūki who launched into a mindless rampage in order to collect some of the beast's cells. Ultimately, with some help from Motoi, Killer B is able to convey his feelings to Fukai who is glad to know that B had found something to fill the void left by being a jinchūriki. As his body deconstructed, Fukai ordered B to end the war. With this, B rushed towards the battlefield noting that his war had just begun.