Kurama (Kai)

The Nine-Tailed Demon Fox (九尾の妖狐, Kyūbi no Yōko) is the most powerful out of all nine of the tailed beasts; a single swipe from just one of its nine tails can create tsunamis and flatten mountains. After the Nine-Tails attacked Konohagakure, Minato Namikaze, the Fourth Hokage, sacrificed his own life by sealing it within his newborn son, Naruto Uzumaki. After after a few of ir previous hosts dies it is sealed within Shouja Tensei.

Appearance
Although the Nine-Tails primarily resembles a demonic kitsune with orange fur and blood-red slitted eyes, it also possesses the upper-body structure of a human, complete with opposable thumbs on its pawed hands. Out of all the nine tailed beasts, the Nine-Tails' form is closest to the form of the Ten-Tails.

Personality
The Nine-Tails is sadistic, cunning, and sarcastic, but it does have a distinct sense of honor and pride, and possesses a loathing respect for Shouja, Naruto and Minato. It will go to great lengths to preserve its own life, as shown when it forces its chakra into Shouja whenever his life is in danger. Back when it was within Naruto, the Nine-Tails became angry and contemptuous at Naruto when he rejected its chakra, although this was merely the rage of missing the opportunity to usurp control over Naruto's mind and body, which would have weakened the seal.

The Nine-Tails has a deep hatred for the Uchiha clan and their Sharingan, Most likely because of the many times Madara manipulated it in the past. It even remarked that Sasuke Uchiha is a lot like Madara because of his power of the Sharingan.

The personality of the Kyūbi drastically changes after he is tamed by Shouja at the Falls of Truth. Shouja and the Nine-Tails appear to be able to speak to each other in a much more relaxed state than Naruto Uzumaki and the Nine-Tails did in times past. For example, when Naruto had a conversation with the Nine-Tails, the latter was in a cage with a special seal keeping it from taking over Naruto. As Shouja is one of the few people who has ever had total control over the Nine-Tails (via his Falls of Truth training), he and the Nine-Tails can talk without such restraints, with Shouja even kicked back relaxing on top of its large snout. The Nine-Tails is shown to get easily annoyed with Shouja's desire to become the strongest ninja in the Leaf Village; however, that is only shown in a comical light.

However, despite Nine-Tails' new friendly relationship with Shouja, the Nine-Tails' main goal, like in times past, remains self preservation. For example, it would more than willing to be released and destroy any threat to Shouja, not really showing any care if Shouja's valued comrades are around to get caught in the crossfire. However, behind the brutal appearance, the Nine-Tails is shown to have a good analytical ability as well as being extremely wise.

History
The Nine-Tails first came into being in the waning days of the Sage of the Six Paths' life; to prevent the Ten-Tailed Beast resurgence, the Sage split up its chakra into nine separate, monstrous constructs of living chakra, which would become known as the tailed beasts. Over the centuries, the Nine-Tails gained a reputation as an age-old natural disaster, appearing at random to attack areas where human malice has collected and festered.

Many decades ago, when Madara Uchiha defected from Konoha, he used his Mangekyō Sharingan to take control of the Nine-Tails, and used it to help him fight against Hashirama Senju, the First Hokage, to exact his revenge. The battle was so great that it tore the earth apart and created the Valley of the End. Despite being in control of the Nine-Tails' power, Madara was defeated. Many years later, the Nine-Tails attacked Konoha. Madara denied that he had summoned it to destroy the village and claimed that the Nine-Tails' attack had been a natural occurrence. During the attack, the Nine-Tails decimated many shinobi that tried to repel it. Minato, riding atop of Gamabunta, was able to defeat the Nine-Tails by sealing it within Naruto. In the anime, it was revealed that the Nine-Tails had left behind large amounts of its chakra during the attack. Kazuma collected and sealed the chakra within his own son, Sora, hoping to make use of its power for his own agenda.

After Naruto's death, it was sealed inside of Shouja Uzumaki.

Abilities
Being the strongest of the nine Tailed Beasts, it is safe to assume that the Nine-Tails has a great amount of power. It has a great amount of defense, shown when it blocked it's former host, Naruto's, Sage Art: Super Great Ball Rasengan with only it's tails, when it survived not one, but two Wind Release: Rasenshuriken, and finally when he resisted Naruto's Sage Art: Super Great Ball Rasengan Barrage. It also has the most chakra out of all of the other Tailed Beasts. The Nine-Tails chakra is so immense, that even after Naruto, and later on Shouja, took it's chakra from it, it was able to form a Menacing Ball several times larger than itself, though both times the technique crumbled as it was resealed.

It has it's own version of the Menacing Ball technique; gathering blood and chakra to form a condensed sphere and then eating it before spitting it out to create a truly massive explosion. It's former host, Naruto, has also pointed out that the Nine-Tails is very fast despite it's enormous size.