Isobu

Isobu, more commonly known as the Three-Tails, is one of the nine tailed beasts. It was last sealed within Yagura of Kirigakure.  Isobu and the tailed beasts first came into being in the waning days of Hagoromo Ōtsutsuki, who used his Creation of All Things Technique to divide the Ten-Tails' chakra into nine separate bodies and giving each a name. Some time after being created, the Sage explained to the young tailed beasts that a link existed between them despite their separation. He also foretold of a day when they would be brought together again - though not as they were - and that at that time someone would emerge to show them what true power is. After Hagoromo's death, the tailed beasts drifted apart, apparently due to Kurama's belief that their number of tails was an indication of their strength. At some point in the past, Isobu, who was in the possession of Kirigakure, was sealed within the body of a kidnapped Rin Nohara of Konohagakure. They plotted for Rin to be taken back to her village as a Trojan horse, releasing the tailed beast to wreak havoc in Konoha. This failed, however, as Rin was fully aware of their schemes and opted to kill herself at hands of her friend and fellow team-mate, Kakashi Hatake before their objectives could come to fruition.

Eventually, Isobu was revived and sealed within its next jinchūriki Yagura, the Fourth Mizukage, who managed to gain complete control and harmony with it. However, when Akatsuki went after it, the beast was in the wild; the story behind how it came to be like this is still unknown. In the anime, Tsunade states that Isobu disappeared after the Third Shinobi World War. Isobu speaks in a timid manner, referring to itself as "boku" which is usually used by young boys. Isobu primarily resembles a large turtle, but with a crab-like shell, spikes all over its body, and three shrimp-like tails. Under its shell, it has red, muscle-like tissue. It has a pair of human-like arms and hands, but no hind-legs. His face is concealed between a large forehead and lower jaw both of which have spikes. Its eyes are red and have crimson pupils. In the anime, the eyes are red with yellow pupils. Its right eye is constantly closed. During the last remaining days of the Sage of Six Paths, Isobu was essentially much the same in appearance, albeit smaller in size with shorter spikes around its body, but was still many times larger than the Sage. As a tailed beast, Isobu possesses an enormous amount of chakra that it can transfer to others and can create the Tailed Beast Ball. It also has the ability to create coral and swim at very high speeds. Kirigakure was confident of its destructive potential that they intended to unleash Isobu in the midst of Konohagakure to destroy the village. In the anime, it could produce a hallucinogenic mist that exploited the victim's insecurities and forced the victim to face them. Isobu can roll into a ball to move about quickly and attack its opponents, making full use of the protrusions on its shell in a manner similar to the Akimichi clan's Spiked Human Bullet Tank. Isobu's tough skin and shell also grant it additional defence, allowing it to withstand nearly all forms of attack. It can also use any of its three spiked tails to strike its opponents and break through most defences. In the anime, Isobu's only known physical weakness is its eye; as tough as its skin and shell are, it cannot harden its eyes and thus seems to keep one closed at all times.

In the anime, Isobu's abilities were greatly elaborated upon. It could create shockwaves to repel attacks and produce large tidal waves around it, enabling it to overwhelm Guren's Crystal Release several times over the course of their battle. When Isobu ate something, thousands of miniature versions of itself would attack what was eaten within its stomach, presumably to speed up the digestion process. It was also shown capable of materialising an entrance to a separate dimension in which it could hide its presence, until it was ready to return to wherever it chooses. As a turtle, Isobu has an affinity for Water Release. In the anime, it has shown to fire powerful water blasts that are capable of destroying an entire cliff side. In the manga, Tobi and Deidara confronted the beast around the same time Naruto Uzumaki had begun his Wind Release training, to which it responded by beginning to chase Tobi. With the Three-Tails distracted, Deidara moulded an explosive clay fish in an attempt to capture it. It was unclear if this marked the end of the battle, as the remainder of the battle went unseen. As the two towed the Three-Tails to the Akatsuki's lair after the battle, Tobi gloated at bringing the Three-Tails down with his special technique, but Deidara thought otherwise. It was later sealed in the sealing statue. In the anime, Orochimaru instructed Kabuto Yakushi and Team Guren to take a young boy named Yūkimaru to a lake. After they arrived, Kabuto forced Yūkimaru to release all of his chakra, which caused the Three-Tails to begin to surface from the lake. With Guren's help, the beast was completely revealed, and they attempted to capture it. Their attempts proved insufficient, however, and the beast created a large tidal wave to wash its attackers away. The tidal wave gained the attention of a nearby group of Konohagakure ninja, who tried to use Four-Corner Sealing Barrier to permanently trap the beast in its own dimension. Just as the sealing began to work, the Konoha ninja were interrupted by Guren, which prompted the beast to attack them all. Yūkimaru was able to calm the beast down temporarily, but, after he became tired, the Three-Tails turned its attention to him. Guren and Naruto Uzumaki came to his defence, but were swallowed in the process. With the help of their allies on the outside, they were able to escape, and the Konoha ninja tried once more to seal the beast. Just when the sealing was almost complete, Yūkimaru, angered by the apparent death of Guren, empowered the beast to break free of its restraints. The Three-Tails went on a rampage, attacking everyone nearby and crushing Nurari, Kigiri, and Kihō. Its attempts to attack Yūkimaru, however, had no effect. It was only through the use of the Wind Release: Toad Oil Flame Bullet that the beast was driven away. The sealing attempt was left to Anbu members, and the remaining Konoha ninja returned home. Deidara and Tobi of Akatsuki soon found these Anbu members and disposed of them.