Naruto's Jinjuriki Transformation

Naruto Uzumaki is the third jinchūriki of Kurama — the Nine-Tails. He is gifted with its enormous supply of chakra, to which Kakashi Hatake estimated it to be a hundred times greater than his own when its influence is not suppressed. Also, depending on the amount of Kurama's chakra he's using, Naruto is given an increase in strength, speed, and his healing factor are pushed to such levels that he completely recovered from a Chidori through his chest in mere moments with no lingering signs of injury. At times, he is also granted a fox-shaped chakra shroud with massive invulnerability, being able to resist being pierced by Orochimaru's Sword of Kusanagi, a sword known as being able to cut through adamantine, and is completely undamaged by the alkali substance excreted by Saiken, which was able to damage Gyūki and disintegrate its surroundings rapidly. Kurama was also believed to be played a role in enhancing the Uzumaki clan's healing ability that Naruto inherited from his mother.

Summary
Due to the Eight Trigrams Seal that his father, Minato Namikaze, the Fourth Hokage, placed on him, it initially allowed a small amount of Kurama's chakra to always mix with Naruto's own. Kurama's chakra first came to Naruto during life-threatening situations, given to him by the fox itself to ensure its survival, but after training with Jiraiya, Naruto learned how to contact Kurama and demand some of its chakra. Alternatively, Naruto could give into his anger or frustration, allowing Kurama to force its influence upon him. Depending on how much he gained, Kurama's influence within its chakra could make Naruto lose control of his senses, devolving into an animal that attacks anything within reach, as well as damaging his own body, slowly shortening his lifespan. Although a number of methods had been devised to break its influence over Naruto (Jiraiya's seal tag,[5] and Yamato's Hokage-Style Sixty-Year-Old Technique — Kakuan Entering Society with Bliss-Bringing Hands, which was facilitated by Hashirama Senju's necklace Naruto wore before its destruction),[6][7] Naruto simply limited his use of Kurama's chakra, and tried not to allow his anger get the better of him, but he eventually attempted to exercise more control over it, in which he was able to achieve during the Fourth Shinobi World War.

After combining his chakra with Kurama's and recently developed a trusting relationship, Naruto and the fox can switch control of his body at will, allowing Kurama to speak through him.[8]

Initial Jinjuriki Form
By simply tapping into Kurama's chakra, Naruto's body begins its initial transformation. His blue eyes become red and pupils become slitted. Following this, his nails and canine teeth grow longer and sharper and his blonde hair will grow longer and spikier, as it stands on end. Naruto's whisker marks will also widen and thicken, adding to his feral appearance. While he can still stand on his own two feet, Naruto can move at greater speeds by manoeuvring on all fours in a manner that looks similar to the Four Legs Technique used by the Inuzuka clan. Depending on how much of Kurama's chakra was unleashed, it was capable of glowing around his body in an untamed way, similar to fire. Until he achieved the Nine-Tails Chakra Mode, it was the only form which resembled flames.

Version 1
During Naruto's battle with Paul Gekko of the Gekko Clan who was taken away by Mecha King Ghidroah, Kurama granted Naruto more of its chakra, which enveloped Naruto's body as a bubbling chakra construct, with one tail, which Jiraiya referred to as the "demon fox cloak" (妖狐の衣, yōko no koromo).[12] Naruto's Version 1 forms had all the initial jinchūriki form's physical traits, but the black rings that surrounded his more berserk-looking eyes were also present. In this form, Naruto could use his elongated, sharpened claws instead of his fists, and run at greater speeds on all fours, making him more beast-like. The chakra itself in this form was noticeably denser than it was in its previous form, going from a gaseous state to a boiling liquid state. The chakra produced by these forms was powerful enough to cause the shadow clones Naruto produced to double over in pain.[13] According to Yuki Uzuki, Naruto's transformations were almost always triggered by his emotional state. The more he was distressed, the easier it was for Kurama to manipulate him through its chakra; its control over Naruto usually corresponds with the number of tails grown. Naruto was able to reach the third tail of Version 1 and remain in control over his body, but will become highly aggressive and dangerous due to the negative influence of Kurama's chakra. Naruto's most powerful weapon in that state was the demon fox shroud itself, and it appeared to have a mind of its own; when a strike that was meant for Paul missed, the chakra itself stretched off of Naruto's arm and managed to hit Sasuke before he had time to react. Since the chakra was sentient, it was extremely difficult, if not impossible, to predict, as Naruto was followed with the Sharingan, but the chakra was not. The shroud granted Naruto some measure of protection, as it could endure attacks like the Fire Release: Great Fireball Technique.[14] Naruto could also use the shroud's chakra arms and tail as grappling hooks to either grab onto objects or enemies from great distances, and use it as a shell to help him create a Rasengan without the help of his shadow clones. However, the shroud was not without its drawbacks; after Naruto used his left arm for a number of attacks against Sasuke, it was left numb from overuse and the constant damage of Kurama's chakra on his body.[15] Despite this, every advantage that the shroud gives Naruto increases in strength with each tail. For example, his roar that simply caused a powerful shock wave in his initial jinchūriki form, created an even more devastating wave of destruction when his third tail grew.

Version 2
During Team Yamato's mission to find Sasuke, the group found and fought Orochimaru, who continually baited Naruto with news of Sasuke. After the three-tailed form was rendered ineffective, Naruto became furious and instantly grew the fourth tail. Within his subconscious, Naruto passed through the gates of Kurama's cage and into its grasp. Its chakra burns through his skin, forming a black sphere that was mixed with Naruto's own blood until the sphere explodes, levelling the area around him and revealing Version 2. Unlike B, who has shown to be able to enter Version 2 with any number of tails, Naruto cannot achieve this form on his own, instead was forced upon his body by Kurama through the weakened seal, which allowed the fourth tail to grow. Once the sixth tail grew, the beast's skeleton began to form out of the chakra. Unlike B, who has shown to be able to enter Version 2 with any number of tails, Naruto cannot achieve this form on his own, instead was forced upon his body by Kurama through the weakened seal, which allowed the fourth tail to grow. Once the sixth tail grew, the beast's skeleton began to form out of the chakra.