Jūgo

, was being held at Orochimaru's North Base, which is also where most of Orochimaru's secret research was conducted. Suigetsu can't stand Jugo and comments that one of the reasons he had to retrieve Zabuza Momochi's sword was because of him. Karin notes that Jugo is mentally unstable, a view confirmed by images of Jugo muttering to himself over who he will kill next, which he determines by gender sometimes. While discussing Sasuke's team with the other members of Akatsuki, Pain refers to Jugo as Jugo of Tenpin (天秤の重吾 Tenpin no Jugo literally "Jugo of the Scales"). Whether this refers to his family or clan name or his place of origin is unknown.

Background
Jugo is the means behind Orochimaru's development of the cursed seals. Some time in the past, Jugo purposely sought out Orochimaru to cure him of his "impulses".It seems that he met and became friends with Kimimaro at this stage. Jugo has trouble controlling his rage, which unexpectedly causes him to transform into a berserk demon (much like a cursed seal does to its user). Upon examination, Orochimaru was able to isolate enzymes in Jugo's blood as the cause of this change. By extracting these enzymes, Orochimaru was able to use them to produce similar, but more controlled, effects in other people.

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 able to mutate his arms to seemingly limitless forms while using his power. When using his ability, he appears to have a dark brownish skin color with huge hands that increase his striking power and his lift power indefinitely. His hands are able to hold people and launch them at high speed and with great accuracy. There are enormous holes in his hands that function as thrusters to increase his power.

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 Juugo 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.

Joining Team Snake
Following his defeat of Orchimaru and recruitment of Suigetsu and Karin, Sasuke Uchiha traveled to Orchimaru's North base to recruit Juugo for his immense power. 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 Team Snake in their mission to hunt down and destroy Itachi Uchiha, Sasuke's brother. Following an encounter with Deidara of the Akatsuki, Juugo discovered a hidden base belonging to the group where Sasuke confronts a clone of Itachi, who challenged Sasuke to meet him at the Uchia Clan Stronghold. Juugo remained behind with the other members of Team Snake with Kisame Hoshigaki as Sasuke confronted Itachi. After Itachi's death and Sasuke's "education" in his brother's true past by Madara Uchiha, Juugo and the other members of Team Snake were reformed into Team Hawk.

Hunt for the Eight-Tails
Having allied themselves with the Akatsuki, Team Hawk was sent to capture the Eight-Tailed Beast so that it could be extracted from its host, Kirābī. Infiltrating the Land of Thunder and the Kumogakure, they confronted Kirābī only to have him defeat Suigetsu. When Juugo attempted to defeat him as well, Kirābī overpowered him using the sword Suigetsu had wielded, which originally belonged to Zabuza Momochi.

Later into the fight, Jugo moved to save the critically injured Sasuke from Kirābī along side Suigetsu. As the two battled Kirābī, Jugo had used his cursed form to pre-launch his body and his allies away from battle. Once far enough from the tailed-beast, Jugo launched the healed Sasuke towards Kirābī. All of Sasuke's attempts failed and left Karin and Suigetsu wide open for a lethal attack. As Kirābī turned to his tailed state, he charged after Karin and Suigetsu. Jugo, alarmed, grabbed Suigetsu and Karin and with explosive power, flew out of the way. He dropped Suigetsu but he saved Karin and both of them went to save Sasuke who was yet again fatally wounded. Karin was about to let Sasuke bite her, but Jugo commented that she did not have enough chakra and let him do the work. Since Sasuke is compatible with the curse mark, Jugo was able to infuse his own flesh to Sasuke's neck and chest that Kirābī tore off, saving his life, but turning him into a child once again like he was when he knew Kimimaro. As Sasuke's Amaterasu flames hit Karin from the Eight Tail's tentacle, Jugo assumed that she has dead given the flames' reputation. He was shocked to see that Sasuke could dose the flames though. He then pulled Karin out of the water and preceided to carry Suigetu and Karin from the fight as Sasuke dragged Kirabi away. He then told Sasuke he knew that he was still injured from Itachi's fight and that they only barely completed the mission.

The Wait for Pain
As his team rest, Jugo hears Suigetsu and Karin bickering about how the other got hurt. He then tells them that they got hurt helping their friends and asks them to stop fighting, because he believes that they are a team and will need each other to suceed. As Karin senses a enemy outside their base, Jugo and Sasuke goes to intercept.

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 creator of the curse seal, he is able to use it to full extent and it will not erode his body. His other mysterious self is also able to throw people using his arm and releasing chakra out the other direction (Apparently using pressurized air to do so). 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.

Trivia

 * The fact that Jugo trusts Sasuke's power can keep him under control as much as Kimimaro suggests that Sasuke as become at least as strong as the latter.
 * Jugo's level loyalty to Sasuke's 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.