Rōshi

was a shinobi of Iwagakure and the jinchūriki of the Four-Tails, Son Gokū.

Background
Rōshi became the jinchūriki of Son Gokū over forty years before the Fourth Shinobi World War at a young age. He left his home town of Iwagakure at some point to better understand and control the power of the beast within him.

Personality
Son Gokū mentioned that Rōshi was just as hard-headed as Ōnoki, the Third Tsuchikage. Despite this, upon observing Naruto Uzumaki's battle against Tobi and his Six Paths of Pain, as well as his knowledge of the tailed beasts final meeting with the Sage of the Six Paths, he came to regrettably believe that all the jinchūriki could have walked down the right path if they were more like the young man. Also despite being Son's jinchūriki for over forty years, he never referred to the beast by its true name, stating that he had not become soft-hearted enough to do such a thing. Before Son was resealed into the Demonic Statue of the Outer Path, he revealed to the beast that he never forgot its name, making peace with the giant monkey.

Appearance
Rōshi had red hair, moustache and beard which tapered off to a point. He was shown wearing a large headpiece consisting of a three pointed crown-like ridge, bearing both his Iwagakure forehead protector, a ring, and a prominent black piece of armour running across his cheeks and the bridge of his nose. He wore a long-sleeved magenta kimono shirt and pants, with mesh-armour shirt and fitted black suit underneath, along with calf-length sandals. Around his waist he wore a brown sash that held a brown armour-like breast plate with a pouch in the front, a brown back plate on the back that is connected to the front with mesh armour, and armoured lapels falling to the sides. Interestingly, his headpiece, hair and beard seemed to model his tailed beast's. After leaving his village, Rōshi discarded his forehead protector and his armour plating battle attire. Instead, he only wore his kimono with a mesh shirt beneath it.

Abilities
Rōshi had been noted to be a powerful shinobi, forcing Kisame Hoshigaki not to play around with capturing him as he was a tough opponent, and leaving Samehada with bad vibes from their encounter. He was also seen using a curved kunai with which it can be assumed that he had proficiency wielding. After his reincarnation and serving as one of Tobi's Six Paths of Pain, Rōshi was equipped with both the Sharingan and Rinnegan. Combining the perceptual and predictive abilities of the former with the shared field of vision ability of the latter, allowed Rōshi to use his attacks in a more precise and coordinated fashion as well as react to enemy attacks more efficiently, both individually and in conjunction and with the other jinchūriki.

Nature Transformation
Like his tailed beast, by combining Fire and Earth Release, Rōshi was able to use Lava Release. With the kekkei genkai, he could spew multiple molten rocks from his mouth, firing them in different directions to make it difficult for an enemy to evade. He is able to create an armour of lava that will burn anyone or anything that comes into contact with him. The armour also increases the damage of his taijutsu attacks to the point that it could burn Naruto in his Nine-Tails Chakra Mode despite not making physical contact with him.

Jinchūriki Transformations
As Son Gokū's jinchūriki, Rōshi was granted a significant amount of its chakra and stamina. The full extent of his control is unknown, but in the anime he could form at least one of Son's tails during his fight with Kisame, further enhancing his power and strength. After being immobilised by B's clone, he transformed into his Version 2 form, in this form, he was able to create an enormous torrent of lava, scorching Gyūki. When Rōshi attacked Naruto and Killer B, Tobi forced him to transform into his Tailed Beast Mode. In this form, he displayed tremendous strength, being able to toss Killer B in his Tailed Beast Mode a considerable distance away.

Itachi Pursuit Mission
After being found by the Akatsuki members Kisame and Itachi Uchiha, the former chose to confront Rōshi alone, leading to the pair fighting. Exploiting Rōshi's weakness to Water Release, Kisame managed to capture the jinchūriki after a difficult battle. Afterwards, his unconscious body was taken by Kisame, who took him to one of his organisation's hideouts, where the Four-Tails was extracted from his body, resulting in his death.

Fourth Shinobi World War: Confrontation
In preparation for the Fourth Shinobi World War, Rōshi was reincarnated by Kabuto Yakushi to fight against the Allied Shinobi Forces, before being mobilised alongside the other deceased jinchūriki. As dawn broke on the second day of war, it was revealed that Tobi had turned the reincarnated jinchūriki into his own customised Six Paths of Pain, with each having a Rinnegan and Sharingan in place of their left and right eyes respectively. Each jinchūriki also had their particular tailed beast resealed within them and a chakra receiver embedded into their bodies.

Fourth Shinobi World War: Climax
Rōshi later travelled together with Tobi, in pursuit of Naruto and Killer B. Encountering their targets, the reincarnated jinchūriki were sent into battle with Rōshi leading the offensive, using his Lava Release: Scorching Stream Rock Technique to pressure the enemy. When this initial assault failed, he, like the others, unleashed the power of their respective tailed beast by materialising the first of its tails. Whilst Naruto and B conversed, Rōshi exploited this opportunity to attack the former directly, after covering his body in lava. Despite evading the strike, Naruto's face was still scorched by the heat, but when Rōshi attacked again, Naruto endured the blow in an attempt to destroy the chakra receiver embedded in Rōshi's chest. However, this was thwarted by Han.

Incapacitated in the wake of the Eight-Tails' devastating attack, after B's recent transformation, Rōshi was then restrained by the latter's sealing technique. However, before the technique's completion, he managed to escape by adopting his Version 2 form, where he then proceeded to burn the Eight-Tails. Regrouping with the other reincarnated jinchūriki, after Kakashi Hatake and Might Guy's intervention, Rōshi charged past the pair towards Naruto and B.

When he clashes with the former, Tobi forcefully transformed him into his full Four-Tails form, where he then proceeded to assault the Eight-Tails. Grabbing one of the beast's tails, Rōshi hurled the two jinchūriki upwards and, after dislodging Naruto in the process, prepared to swallow him. However, despite Naruto's efforts to lodge himself between the beast's jaws, and B's attempts to restrain the ape, the former is ultimately swallowed whole. While Naruto conversed subconsciously with Son Gokū, Rōshi resisted B's efforts to free his captive comrade, only to be forced to eject Naruto when the young man multiplied. He then tried to impede Naruto from removing the chakra receiver embedded in the beast's chest, but failed to do so thanks to a coordinated strike, leaving Rōshi's incapacitated body behind as Son Gokū was resealed into the Demonic Statue of the Outer Path.

When a transformed Naruto's Tailed Beast Ball later clashed with the collaborative one formed by the other tailed beasts, Rōshi's unconscious body was protected by the Eight-Tails from the resulting blast. Afterwards, Naruto subconsciously met with the other beasts and their jinchūriki, where it was revealed that shortly before Son was resealed, Rōshi questioned his beast as to whether it thought they too had taken the wrong path during life. He then stated that despite not being considerate enough to have spoken it, he had not forgotten the beast's real name. As the two fade away, a smiling Rōshi asked the beast if calling it "Son" would be all right. After Son was resealed into the Demonic Statue of the Outer Path, Rōshi and the other jinchūriki's corpses were collected by B and held in Gyūki's tentacles. With the release of the Impure World Reincarnation, Rōshi and the others are enveloped in a light of sorts before their bodies start to deconstruct and Rōshi's soul returned to the afterlife.

Trivia

 * The name "Rōshi" is made up of the kanji for and . It can also mean.
 * Rōshi's name was also used by the mentor and master of Son Gokū from Akira Toriyama's manga series Dragon Ball, the latter of which could transform into a giant ape-like monster after gazing at the full moon and whom the Biju Son Gokū was based off of.
 * In order to prevent the jinchūriki from turning traitor, it is tradition for the host to be selected from the family of the village's own Kage. It might be that Rōshi somehow was connected with one of the Tsuchikage. Due to Son mentioning Onoki with some familiarity, its possible that Rōshi had some relation with him.
 * In the manga, Rōshi's headpiece is depicted as having a golden ring on the left side. The golden ring on Rōshi's headpiece was not present in the anime. This was later added as of episode 256.