|“||So that's what happened. No wonder I don't remember it... I was trapped inside of Orochimaru's Genjutsu.||„|
|~ Gyūki realized what happened 30 years ago|
|“||Me? Well. I think I'm going back to Bee. Even his annoying rap has ended up growing on me.||„|
|~ Gyūki to Kurama about returning to Killer Bee due to his raps|
It is voiced by Travis Willingham in English dub and Masaki Aizawa in Japanese dub.
Gyūki is an ushi-oni with four long horns on its head, similar to that of a Jacob sheep. As a tailed beast, it is extremely massive, dwarfing entire forests and towers over large rock formations and buildings and matching the Giant Squid in size. The lower left part of its horns was permanently sliced off in a battle with A, and the right horns were destroyed by its own point-blank Tailed Beast Ball when fighting the Ten-Tails. It also has straight teeth, one of which was blown off during the point-blank Tailed Beast Ball. Following the Fourth Shinobi World War, it grew another tooth, along with its horns (albeit not completely). Gyūki also has a muscular upper-body structure, with a hunched back similar to an American bison, arms with spiked protrusions on the elbows, and hands with opposable thumbs like that of a human. Instead of hind-legs, its lower half consists of its eight tails, which resemble the cephalopod arms of an octopus. These tails will grow back in the event they are sliced off. During the last remaining days of Hagoromo Ōtsutsuki, Gyūki was smaller and its horns were much shorter.
Gyūki is characterized as a tough and serious individual. It uses "ore" (オレ) when referring to itself and often speaks in a somewhat rude dialect. Gyūki was also shown to have a good analytical ability, as it told Killer B that if he left Ponta and Sabu and ran away from them, Kisame Hoshigaki and his water dome would follow him and they (Sabu and Ponta) would be freed. Although Gyūki mentioned that it and its brethren disliked Kurama for its arrogance and belief that their strength are based on their number of tails, it insisted that was no reason for not helping Naruto Uzumaki to control Kurama's power, hinting a benevolent side. Since then, both Gyūki and B have taken a liking to Naruto. Despite his strong bond with B, Gyūki got disgusted by B's annoying raps even after being free from Kaguya he getting use to it.