Jūgo

, was being held at Orochimaru's North Base, which is also where most of Orochimaru's secret research was conducted. He is recruited as a member of Taka.

Background
Jugo's personality is usually quiet and unassuming, but when angered, those around him stand little chance of survival. One time he even became so angry that he devoured an entire village. This has caused a fearful village to label him as the "Scales", where anything could tip the balance. Cursing his existence, he took to secluding himself in caves, hoping to bring no one any harm. This lasted until Kimimaro came to him, who was himself the last remnant of his own Kaguya clan. Following Kimimaro, Jugo allowed himself to be one of Orochimaru's test subjects. Upon examination, Orochimaru was able to isolate enzymes in Jugo's blood that caused him to transform. By extracting these enzymes, Orochimaru was able to use them to produce similar, but more controlled, effects in other people, leading to the creation of the cursed seal. As time passed, Kimimaro died, then Orochimaru followed him, and Jugo shut himself away once more.

Appearance
Jugo has a bracket-shaped symbol on his left palm. Whether or not this is also present on his right palm or if it has any significance has yet to be seen. He is the tallest known, non-animal character in the series (202 cm). Jugo wears a black shirt, tan pants, and a blue cloak. After Taka has allied with Akatsuki, Jugo was shown wearing an Akatsuki robe.

Personality
While Jugo initially appears quite bloodthirsty, Karin notes that this is only common behavior when he is enraged; Jugo himself doesn't want to kill anyone. Jugo's fits of rage are random and thus the reason why he willingly remains confined. The only reason he agrees to go with Sasuke is because he views Sasuke as the only person capable of preventing him from killing people while enraged, by the means of killer intent or the Sharingan. Before Sasuke, it was Kimimaro who kept Jugo in check and as Kimimaro was the only person Jugo came into any contact with, the two grew close. After hearing that Kimimaro sacrificed his life to deliver Sasuke to Orochimaru, Jugo believes that Kimimaro's spirit continues to live on in Sasuke.

Suigetsu can't stand Jugo and comments that one of the reasons he had to retrieve the Decapitating Carving Knife was because of him. Karin notes that Jugo is mentally unstable, a view confirmed when Jugo was muttering to himself over who he would kill next, which he would determine by gender. While discussing Sasuke Uchiha's team with the other members of Akatsuki, Pain refers to Jugo as, referencing his dual personality. The English manga uses the term "bipolar Jugo", obtaining the same effect.

Joining Hebi
After defeating Orochimaru and recruiting Suigetsu and Karin, Sasuke traveled to Orochimaru's North Base to recruit Jugo. Initially unwilling to join forces with Sasuke, Jugo tapped into his Cursed Seal, but was then frightened into releasing it by Sasuke's killer instinct. He then joins the newly formed Hebi in their mission to hunt down and kill Akatsuki's Itachi Uchiha, Sasuke's brother. Jugo discovered a hidden base belonging to the Akatsuki where, where Sasuke confronts a clone of Itachi, who challenged Sasuke to meet him at the Uchiha Clan Stronghold. Jugo remained behind with the other members of Hebi and Kisame Hoshigaki as Sasuke confronted Itachi. After Itachi's death and Sasuke's "education" in his brother's true past by Madara Uchiha, Jugo and the other members of Hebi were reformed into Taka, allies of Akatsuki.

Hunt for the Eight-Tails
Having allied themselves with the Akatsuki, Taka was sent to capture the Eight-Tailed Beast so that it could be extracted from its host, Kirābī. Infiltrating Kumogakure, they confronted Kirābī only to have him defeat Suigetsu. When Jugo attempted to defeat him as well, Kirābī overpowered him using the sword Suigetsu had wielded, which originally belonged to Zabuza Momochi. When their team starts working together, Jugo concentrates on removing his teammates from danger. After Sasuke is critically injured Jugo infuses some of his flesh with Sasuke to heal his wounds. This reduces him to a younger appearance. Sasuke is eventually able to capture Kirābī, and he recuperates with the rest of Taka.

The Wait for Pain
As Taka rested in one of Alatsuki's hideout, Karin sensed a spy has followed them. Jugo and Sasuke went and intercepted him, and left the hideout for a new one shortly after.

When Nagato died after his final talk with Naruto, Sasuke was seen in his hideout, telling his teammates to prepare for their attack on Konoha.

Abilities
His brief fight with Sasuke and Suigetsu revealed that Jugo can control his transformation, unlike the static effects of a standard cursed seal. When battling Sasuke, he changes his left arm into a piston-like ram to increase his punching power and then alters it into a massive blade from his forearm to fight Suigetsu. He is also capable of doing only a partial transformation, invoking a level two form over one portion of his body without completely changing. Also, since Jugo is the very origin of the curse seal, he is able to use it to its full extent without it eroding his body.

Jugo's other personality is able to throw people by using his arm and releasing chakra out the other direction. This can also be used for escaping, charging right out of the battle with great speed. Finally, Jugo is able to understand animals, such as birds (apparently because of his cursed seal), using them as scouts and to help him accomplish tasks. He also can fuse part of his body, while in Cursed Seal form, to replace parts of other Cursed Seal-infected people's bodies, as he does to Sasuke. However, the downside to this appears to be it reverts Jugo to the appearance of a child.

Trivia

 * Jugo's level of loyalty to Sasuke is similar to that of Kimimaro's loyalty to Orochimaru, as Jugo showed himself willing to risk his life to save Sasuke's just as Kimimaro willed his dying body to aid Orochimaru in obtaining Sasuke.
 * Jugo is the oldest member of Taka.
 * Anko Mitarashi, who is ten years older than Jugo, was given one of Orochimaru's cursed seals in her youth indicating how long Jugo has been in Orochimaru's care.