Because of the demon fox sealed within him, Naruto has access to its great reserves of chakra, a form of energy which allows ninja to perform supernatural feats. This surplus of chakra allows him to perform ninja abilities that someone of his age would ordinarily be incapable of using. Though portions of the fox's chakra constantly mix with Naruto's own Naruto can forcibly draw upon its reserves by either submitting to rage or by directly asking the fox for a donation of its strength. Once the demon fox chakra releases, a fox-shaped shroud envelops Naruto, with the number of tails, ranging from one to nine, indicating its current state of release. While each tail drastically increases his fighting strength, Naruto begins to lose his rationality as more tails appear, completely losing himself once the fourth tail appears. Because the demon fox's power can quickly become a danger to those he cares for, Naruto attempts to limit his reliance on and usage of the power.
Naruto takes advantage of his expanded chakra reserves throughout the series. His first and most recurring example of this is the Shadow Clone Technique, which creates any number of physical copies of the user, but requires large amounts of chakra. Though most ninjas can create only a few shadow clones, Naruto's vast chakra allows him to create hundreds of clones at once without worrying about fatigue. He finds a number of uses for these clones, among them overwhelming opponents, scouting large areas, and training in a short period of time. His ability to summon toads to aid him in battle relies on the fox's chakra, since he can only summon larger toads with the fox's help. He also learns senjutsu, a power-enhancing ability derived from frogs and involving the gathering of natural energy.
Naruto favors the Rasengan, a concentrated orb of spiraling chakra first created by his father. When performing the technique, Naruto creates shadow clones to help him manipulate the chakra into its proper shape. While capable of grinding into whatever it touches and causing great damage, Minato created the Rasengan with the intention of infusing it with his own elemental chakra. Through repeated training with his shadow clones, Naruto infuses the Rasengan with his own wind chakra. This results in the creation of the Wind Style: Rasenshuriken (風遁・螺旋手裏剣 Fūton: Rasenshuriken), which damages anything it impacts on a devastating scale but, when first used, also injures Naruto's arm to a lesser extent. Through his sage training and mastery of Senjutsu, Naruto solves this problem by learning to throw the Rasenshuriken at his targets rather than ramming it into them.
