Isobu (Giyo)

Isobu (磯撫, Isobu), more commonly known by its alias as the Three-Tails (三尾, Sanbi), is a tailed beast that was formerly sealed in Yagura of Kirigakure, after being sealed in Rin Nohara as part of Kirigakure's plan to attack Konohagakure. It has been captured by Deidara and Tobi, then sealed by Akatsuki. He was later resealed into a reincarnated Yagura during the Fourth Shinobi World War. After the war, the beast was released into the wild, where he was fought and captured by Getsu's naval forces, and sealed into Giyo, its current jinchūriki.

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 that would come to be known as tailed beasts 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 and forms than they did. Then, when the time came, they would know what true power is.

At some point in the past, Isobu, who was in the possession of Kirigakure, was sealed within 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 Kakashi before their objectives could come to fruition. Eventually, Isobu was revived and sealed within its next jinchūriki — 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.

Tsunade states that Isobu's disappearance happened after the Third Shinobi World War.

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 yellow 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.

Personality
Isobu speaks in a shy manner, referring to itself as 'boku' (ボク). He is a very kind beast, only angered when shown unfairness by humans. Once angered, it can take a long time to change its beliefs on people, ideas or events. This is evident with Giyo. But for the most part, Isobu is a caring tailed beast, who usually only uses violence when necessary.