Isobu (Kai)

, more commonly known as the, is a tailed beast that was formerly sealed in Yagura of Kirigakure. It has been captured by Deidara and Tobi, then sealed by Akatsuki. It was later resealed into a reincarnated Yagura during the Fourth Shinobi World War.

Background
Isobu first came into being in the waning days of the Sage of the Six Paths, who used his Creation of All Things ability to separate the Ten-Tails' chakra from its body and divide it into nine separate constructs in order to ensure that it would never resurface after his death.Some time after being created, the Sage sat down with all the young tailed beasts and told them that they would always be together even when separated, and that one day they would become one entity again with different names as well as forms than they did then when the time came for them to understand what true power is.

At some point in the past, Isobu fell into the possession of Kirigakure and was sealed within Yagura, the Fourth Mizukage.However when Akatsuki went after it, the turtle was in the wild; the story behind how it came to be like this is still unknown. It was also stated by Tsunade in the anime that Isobu disappeared after a great war.

Personality
Isobu speaks in a shy manner, referring to itself as which is usually used by young boys.

Appearance
Isobu primarily resembles a large turtle, but with a crab-like shell, 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. Its lower jaw is rather big and has teeth-like horns, together with its big forehead, which also has horns, it somewhat resembles a mouth with big teeth, making it look like the rest of the face is inside the mouth. Its eyes are dark and have red pupils. In the anime, the eyes are red with green pupils. Its right eye is constantly closed, indicating some sort of injury, and because of this, it is particularly vulnerable to attacks directed at its right eye. During the last remaining days of the Sage of the Six Paths, Isobu was much smaller than it currently is but was still many times larger than the Sage.

Abilities
Isobu has the ability to create coral, and swim at very high speeds. Like all tailed beasts, it has an enormous amount of chakra compared to most ninja and can form the tailed beasts' ultimate attack, the Tailed Beast Ball. Tobi suggested that Kisame would have been a better choice for capturing the beast, given its affinity for water. Deidara claimed that because Isobu lacked a host, it couldn't control its own strength. Isobu has also been shown to be able to roll into a ball and attack its opponents, making full use of its shell and its many protrusions in a manner similar to the Akimichi clan's Spiked Human Bullet Tank. Its tough skin and shell also provides additional defence for the beast, allowing it to withstand most kinds of attacks.

Trivia

 * literally means 'beach stroker', and is also an adaptation of the name of the.
 * Turtles are often used as the base design for sea monsters in Japanese folklore. Isobu's design in particular was conceived as a result of the series creator, Masashi Kishimoto's, interest in monsters, yōkai, and kaijū, mixing together various elements of those types of creatures to create a monster with a turtle's body and a shrimp's tail with a crab-looking figure.