Juugo

重吾

Juugo is the largest of the three members making up Sasuke Uchiha's new team, Snake (now known as Hawk). Juugo was held at Orochimaru's North Base, where most of Orochimaru's secret research took place. Suigetsu dislikes Juugo and remarks that one reason he had to retrieve Zabuza Momochi's sword was because of him. Karin observes that Juugo is mentally unstable, a view supported by images of Juugo muttering to himself about who he will kill next, a decision he makes based on gender.
Juugo is the basis for Orochimaru's development of the cursed seals. At some point in the past, Juugo deliberately sought out Orochimaru to cure his "impulses." Juugo struggles to control his rage, which unexpectedly causes him to transform into a berserk demon (similar to how a cursed seal affects its user). Upon examination, Orochimaru isolated enzymes in Juugo'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.
Although Juugo initially appears quite bloodthirsty, Karin notes that this is merely common behavior for the enraged; Juugo himself does not want to kill anyone. Juugo's fits of rage are random, which is why he willingly remains confined. The only reason he agrees to go with Sasuke is that he views Sasuke as the only person capable of preventing him from killing people while enraged. Before Sasuke, it was Kimimaro who kept Juugo in check, and since Kimimaro was the only person Juugo interacted with, the two grew close. After hearing that Kimimaro sacrificed his life to deliver Sasuke to Orochimaru, Juugo believes that Kimimaro's spirit continues to live on in Sasuke.
Juugo has a bracket-shaped symbol on his left palm. Whether this symbol is also present on his right palm or if it has any significance remains to be seen. His brief fight with Sasuke and Suigetsu revealed that Juugo 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 performing only a partial transformation, invoking a level two form over one portion of his body without completely changing.
While discussing Sasuke's team with other members of Akatsuki, the Akatsuki leader refers to Juugo as Juugo of the Scales (Tenbin no Jūgo, with "scale" referring to something that determines balance). Whether this is a title or a location is unclear.
After Team Snake is dispatched on their mission into the forest, Juugo begins his search by activating his special enzyme and asking a bird for information.