Gyuuki

牛鬼, 八尾

The Eight-Tails is a tailed beast sealed within Killer B of Kumogakure, following the failures of his cousin, his cousin's uncle, and his cousin's father.
Because Killer B is one of the few jinchūriki to gain control over his tailed beast, his relationship with the Eight-Tails is very relaxed. While the Nine-Tailed Demon Fox constantly threatens its jinchūriki and must be restrained or confined to be spoken to, B and the Eight-Tails can talk leisurely, with Killer B even sitting on its nose. However, B tends to annoy the Eight-Tails to comical effect; his serious and no-nonsense demeanour often contrasts with B's tendency to goof off whenever he likes, adding fuel to the Tailed Beast's irritation with his vessel. As a result, the Eight-Tails is not above bad-mouthing B. The Eight-Tails is also known to scold him on serious occasions, as shown when it criticised B for rapping during his fight with Kisame when he should have been completely focused on their opponent. Because of this, the Eight-Tails appears to be much more noteworthy than B regarding responsibility. Before B learned to control it, the Eight-Tails was infamous for being wild and violent. It also went on many rampages whenever its former jinchūriki would lose control of it.
Despite the Eight-Tails' strong relationship with Killer B, its main goal, like that of the other beasts, is self-preservation. For example, it was more than willing to be released and attack Kisame Hoshigaki despite Sabu and Ponta being close by. The Eight-Tails is also shown to have good analytical ability, as it told Killer B that if he left Ponta and Sabu and ran in the opposite direction, Kisame and the water would follow him, and they (Sabu and Ponta) would be freed. The Eight-Tails mentioned that it used to be much more aggressive and violent but that Killer B changed it. It also said that it doesn't like the Nine-Tails but insisted that was no reason for B to refuse to help Naruto take control of the beast, hinting at a benevolent side. Since then, both the beast and B have taken a liking to Naruto. The Eight-Tails also tends to reprimand B. This is usually shown in a comical manner, as when it bumped B in the head when the latter started to mention in a perverted manner how Yugito's chakra receivers were embedded in her left breast.
With regards to its relationship with the other tailed beasts, the Eight-Tails maintains that they have their own emotions and personalities. It has expressed dislike of the Nine-Tails' habit of ranking their strength based on their number of tails and has also stated that seeing another beast being forcefully controlled angered the rest of them greatly.