Jūgo

is a shinobi from an unknown clan, who was being held at Orochimaru's Northern Hideout which was also where most of Orochimaru's secret human research was conducted. Jūgo was said to have gone to Orochimaru of his own free will, hoping that Orochimaru would cure him from his rages. He was later recruited as a member of Sasuke Uchiha's group Taka, which was initially called "Hebi" at the time of its creation.

Background
An outcast, Jūgo's rage made him a danger to anyone around him, as they stood little chance of survival should he lose his temper. At one point, he became so angry that he destroyed a village and all of its inhabitants. This has caused others 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 he met Kimimaro, who was himself the last remnant of the Kaguya clan. Following Kimimaro, Jūgo allowed himself to be one of Orochimaru's test subjects in the hopes that he could be cured of his fits of rage.

However, amazed by Jūgo's ability to absorb natural energy to undergo various drastic physical alterations at the cost of mental state, Orochimaru's attempts to discover the origin of his clan's ability to use such power led him to the Ryūchi Cave, where he learned Sage Mode. But unable to use Sage Mode properly, Orochimaru instead devised the cursed seals by combining his Senjutsu chakra into the mutative enzymes he isolated from Jūgo's blood. As time passed, Kimimaro died, and Jūgo shut himself away once more.

Personality
While Jūgo initially appeared quite bloodthirsty, Karin noted that this was only common behaviour when he was enraged; Jūgo himself didn't want to kill anyone and in reality he is a very gentle person. His fits of rage are random, and thus are the reason why he willingly remains confined. The only reason he agreed 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 Jūgo in check, and as Kimimaro was the only person Jūgo came into any contact with, the two grew close. After hearing that Kimimaro sacrificed his life to deliver Sasuke to Orochimaru, Jūgo believes that Kimimaro's spirit continues to live on in Sasuke, and thus is completely loyal to him, even after Taka had been disbanded, and Sasuke left them in the Land of Iron, Jūgo made his way back to Sasuke and matter-of-factly noted when asked, that his place was beside Sasuke as his shield.

Suigetsu couldn't stand Jūgo at first, and commented that one of the reasons he had to retrieve the Kubikiribōchō was because of him. Karin noted that Jūgo is mentally unstable, a view confirmed when Jūgo was muttering to himself over whom he would kill next, which he would determine by gender. While discussing Sasuke Uchiha's team with the other members of Akatsuki, Pain referred to Jūgo as, referencing his dual personality. According to the third databook, he is cowardly (in his normal state) and violent (when natural energy overtakes him). He has also been described as one who "does things at his own pace".

Appearance
Jūgo is a tall, muscular young man who has spiky orange hair, red-orange eyes and a usually calm disposition. However, when affected by his murderous side, his skin turns dark, his irides becomes a pale yellow colour while his sclerae turns black, and he grows various weapons and appendages to suit his battle combat situation, as well as having a deranged look. Jūgo has a bracket-shaped symbol on his left palm. When Jūgo was first introduced, he wore a pale blue shirt and pale green shorts. Later when Tamaki tried to find him some clothes, he wore black pants, a tan shirt and brown sandals. After Taka had allied with Akatsuki, Jūgo was shown wearing an Akatsuki robe.

Abilities
While it is unknown if Jūgo ever received any formal shinobi training, he is still a very dangerous individual, enough to warrant the attention of other powerful ninja such as Orochimaru and Sasuke, with both of them searching Jūgo to join them at separate times. After adapting their DNA and abilities, Kabuto also indirectly praised Jūgo when noting the quality of Sasuke's former team.

Jūgo is able to understand and communicate with animals, such as birds, and is able to request them to help him accomplish tasks, such as acting as scouts or gathering information they have already witnessed. These informations are shared in a great speed, allowing Jūgo to know about things that happened in a far away distance.

He can also transfer his chakra onto others, as seen when he infused Sasuke's Susanoo with senjutsu chakra.

Sage Transformation
Like other members of his clan, Jūgo possesses the ability known as Sage Transformation which allows him to use the natural energy he absorbs to transform his body at will. He can change what form he takes almost instantly and can isolate the transformation to specific parts of his body. Also due to this, Jūgo's possesses massive reserves of powerful chakra. However, because he absorbs natural energy constantly, he and his clansmen are prey to sporadic and involuntary surges of rage.

As a result, Jūgo has changed his body into a number of forms. At his début, he changed his left arm into a piston-like ram to increase his punching power, and then altered it into a massive axe blade to counter Suigetsu's sword. While Taka was fighting Killer B, Jūgo formed a set of arm-boosters to both throw his team-mates a large distance and to produce stronger punches. He also created another set of boosters on his back to increase his jumping speed. Jūgo is also capable of extending one of his arms to great lengths to catch targets several feet away from him. Aside from his shape-shifting powers, Jūgo's physical abilities, such as his speed, strength and endurance are also enhanced in proportion to the level of the transformation.

If he fully transforms, Jūgo gains a massive power boost but loses his mind to his murderous side, signified by a change in his voice. When transforming, Jūgo's skin turns dark and his sclera turn black. He also gains a black stripe running from the middle of his forehead and down the bridge of his nose. In this full form, Jūgo is incredibly resilient, being able to take a punch from the Fourth Raikage that penetrated both his arm and chest, yet still managing to retaliate almost immediately with ease despite the injury. In this form, he turned his arm into a shield to defend himself and created a number of chakra cannons on his back that were capable of devastating the area.

Jūgo's clan abilities serve as the origin of Orochimaru's Juinjutsu that he brands his various followers with, which were created using Jūgo's own bodily fluids that were then injected into the intended individual. As such, he is able to use its power to its full extent without it eroding his body. Unlike those who have been given a cursed seal, Jūgo is not limited to one transformation, and can enter whatever form is best for the situation. Jūgo considers those who have received one of Orochimaru's cursed seals to be one of his "copies" and, since they have proven compatible with his own DNA, he is able to give them some of his flesh to heal their injuries. This has the side effect of shrinking him and giving him an overall younger appearance. He can similarly consume others to heal his own injuries and return him to his original 'adult' form, though they do not need to be cursed seal recipients.

Itachi Pursuit Arc
After defeating Orochimaru, and recruiting Suigetsu and Karin, Sasuke Uchiha travelled to Orochimaru's Northern Hideout, to recruit Jūgo. Initially unwilling to join forces with Sasuke, Jūgo tapped into his ability, but was then frightened into releasing it by Sasuke's killer intent. He then joined the newly formed Hebi in their mission to hunt down and kill Akatsuki's Itachi Uchiha, Sasuke's older brother.

Jūgo would later discover multiple hidden bases belonging to the Akatsuki, where Sasuke confronted a clone of Itachi in one of them, who challenged Sasuke to meet him at the Uchiha Hideout. Jūgo remained behind with the other members of Hebi and Kisame Hoshigaki as Sasuke confronted Itachi.

Invasion of Pain Arc
After Itachi's death, and Sasuke's "education" in his brother's true past by Tobi, Jūgo and the other members of Hebi were reformed into Taka. Having allied themselves with the Akatsuki, Taka was sent to capture the Eight-Tails, so that it could be extracted from its host, Killer B. Infiltrating Kumogakure, they confronted Killer B, only to have him defeat Suigetsu. When Jūgo attempted to defeat him as well, Killer B overpowered him using the sword he stole from Suigetsu.

After Sasuke was critically injured, Jūgo tells Karin that she did not have enough chakra to heal him and starts to infuse some of his flesh with Sasuke's, to heal his wounds, saying it would work as Sasuke was compatible with the cursed seal (and hence Jūgo's own DNA). This however somehow reduced him to a younger appearance. When their team started working together, Jūgo concentrated on removing his team-mates from danger, even though he initially objected to rescuing Karin, as he thought she would die from Sasuke's Amaterasu.

Sasuke was eventually able to capture Killer B, albeit a fake, and Jūgo recuperated with the rest of Taka. As Taka rested in one of Akatsuki's hideouts, Karin sensed J|a spy had followed them. Jūgo and Sasuke went and intercepted him, and left the hideout for a new one shortly after.

Five Kage Summit Arc
Taka later set out for Konoha. On their way they were intercepted by Tobi who informed them that Konoha had already been destroyed. Zetsu, who suddenly appeared, then explained that a man named Danzō had been named Hokage. As per Tobi's advice and orders, Sasuke changes their goal to the Kage Summit. Taka is then guided by Zetsu, who had split up into two bodies.

Jūgo and the rest of Taka arrived at the Land of Iron, and after Suigetsu scouted the area and reported there are many guards, Sasuke tells Jūgo to use animals to find the least guarded route. Their presence is soon discovered and Sasuke engages the samurai that come after them. When Karin becomes preoccupied worrying about Sasuke, Jūgo tells her to continue looking for Danzō while he goes to help Sasuke.

Taka is attacked by Kumo-nin that Jūgo identifies as two jōnin and the Fourth Raikage. Knowing their presence will make it difficult for Karin to locate Danzō without exposing herself, Jūgo resolves to killing them. He fully transforms into his cursed seal level 2 and goes into his murderous mental state. The Raikage quickly overwhelms him and forces him into a wall, punching through a defensive shield on his arm and into his chest. Though he has seemingly been killed, Jūgo smirks and aims dozens of boosters from his back straight at the Raikage, firing them at point-blank range. Believing the Raikage to be dead, Jūgo prepares to attack someone else, but he is then hit again by the Raikage with a sudden elbow strike. Jūgo smashes against the wall and seems to be knocked unconscious.

As the battle unfolds, Sasuke destroys the room they are in and Jūgo, having regained consciousness, is buried in rubble. He absorbs the body of a nearby samurai, healing his wounds and returning him to an adult state. He is later seen with Suigetsu, who suggests that they follow the Raikage and Sasuke. Jūgo tells him not to do so because they would be killed. However, Suigetsu says that he has a plan in mind. They try dressing up as samurai to flee the area, but are quickly discovered and imprisoned by the samurai.

Shinobi World War Arc
As the war was being waged, Suigetsu and Jūgo escape their cell in the Land of Iron, having taken care of the guards, and stating that security had gotten looser. Jūgo thinks they should look for Sasuke, but settles for helping Suigetsu find his sword. They also decide they should look for Karin.

When they are unable to find Suigetsu's sword, Jūgo asks Suigetsu why he is so serious about it. Suigetsu tells him a bit about the Seven Ninja Swordsmen of the Mist, telling him about its swords and those who wielded them in the past. Jūgo learns that it's Suigetsu's dream to reform the Swordsmen, and to become their leader. Suigetsu also states that he is nicer than Karin.

Jūgo and Suigetsu escape from the samurai compound. They walk through a forest and discuss their plans. As Jūgo wonders if Karin and Sasuke were all right, Suigetsu tells him that even if they reunited with Sasuke and Karin, it wouldn't be a grand reunion of sorts as Karin wanted Sasuke to herself in order to seduce him. As they continue onwards, Jūgo asks if they would continue looking for swords or find Sasuke and Karin, Suigetsu tells him that they'd continue to get in Karin's way which was his second favourite thing to do after collecting swords. They proceed to head towards one of Orochimaru's hideouts.

After receiving intelligence from the birds about the war that was currently going on, Jūgo questions Suigetsu's motives for staying with Taka. During their conversation, Jūgo loses control of himself and violently attacks Suigetsu sending the upper half of his watery body crashing into a wall. This reveals Orochimaru's secret room and with it, information that Suigetsu claims will be beneficial to them.

Ten-Tails Revival Arc
Later, when Sasuke was being tormented by thoughts concerning what he was, Jūgo and Suigetsu break through the ceiling and enter. Suigetsu examines Kabuto's body while Jūgo examines Anko, the latter stating that she is alive. When Sasuke asks them their purpose of coming there, Suigetsu hands him the scroll — the one with which he exclaims that their group Taka can rule the world with — and making him cognisant of reincarnated Madara's presence even though Itachi forced Kabuto to release Summoning: Impure World Reincarnation, which leaves Sasuke somewhat surprised. Jūgo later helped Sasuke in reviving Orochimaru by giving Sasuke a portion of Kabuto's modified reptilian flesh. Despite Suigetsu's vehement opposition to this, Jūgo simply noted that he would carry out Sasuke's will — a will he believed by extension was that of Kimimaro.

With Orochimaru revived, the team headed towards Konohagakure with the Sannin, where they sensed Naruto Uzumaki's chakra leagues away but pressed on nonetheless at Sasuke's behest. Heading silently towards a dilapidated temple, and then back through Konoha, Jūgo used the natural energy from his Sage Transformation on Orochimaru's cue, to activate the spores that were attached to Sasuke, shrinking in the process. Moving to subdue one of the spare clones, Jūgo absorbed the clone regaining his normal size. With this, he looked on as the four previous Hokage that are reincarnated before him. Listening on silently throughout the proceedings, Jūgo is shocked when Tobirama unleashed a swell of killing intent when he heard Sasuke's intentions to exact revenge on Konoha. Moving almost instinctively, Jūgo moved in front of Sasuke until the situation was quelled by Hashirama. When Sasuke decides to aid the Allied Shinobi Forces after hearing Hashirama's story, Jūgo accompanies Sasuke to the area of the battlefield where Sasuke's former team-mates are.

With the situation looking grim as the Alliance was trapped in a barrier with a Tailed Beast Ball-firing tree, Jūgo made his way back over to Sasuke and noted that they needed to get away, and called for Sasuke to use his Summoning Technique to escape. They are, however, stopped by naruto who demands they stand before him so he could given them his chakra. Jūgo later found himself safe and outside the barrier where he questioned what Naruto had done and listened on as it was explained how Naruto and Minato's actions had saved them. Jūgo subsequently watched on as the Shinju attacked and killed the shinobi around them. As Sasuke then began his next attack against Obito, now knowing that the jinchūriki was vulnerable against senjutsu, Jūgo transferred some of his natural energy into Sasuke, who then proceeded to channel it into his complete Susanoo in a manner similar to the Cursed Seal of Heaven.

Trivia

 * In the Japanese version of Sha no Sho, his name is written as "Jyuugo".
 * According to the databook(s):
 * Jūgo's hobbies are forest bathing and playing with birds.
 * Jūgo's favourite foods are small fish and beef and he dislikes chicken.
 * Jūgo himself doesn't want to fight. However, when affected by his murderous side, he would fight anyone.
 * Jūgo's personality has been described as cowardly and violent.
 * Jūgo's favourite phrase is.
 * Jūgo has not completed any official missions.

Quotes

 * (To Sasuke) "I can't let you die… You're all I have left to remember Kimimaro."
 * (To Suigetsu) "Sasuke's will is Kimimaro's will. And I obey it."