Wind Release: Rasenshuriken

The Wind Release: Rasenshuriken is a shuriken-shaped variant of the Wind Release: Rasengan.

Overview
The Rasenshuriken was invented by Naruto Uzumaki shortly after he figured out the principles of the Wind Release: Rasengan. Like that technique, Naruto typically has the help of two shadow clones in the Rasenshuriken's formation: he provides the chakra, one clone helps keep the chakra contained, and the second clone adds his wind-nature. Unlike the Wind Release: Rasengan, additional shape transformation is applied to the Rasenshuriken, creating four large points around the central Rasengan-core, giving the appearance of a fūma shuriken. By the time of The Last: Naruto the Movie, Naruto is able to create Rasenshuriken without aid.

Rasenshuriken require a great deal of chakra to perform: Naruto has been shown creating as many as three Rasenshuriken on his own before tiring out. While in Sage Mode, he can create two Rasenshuriken per transformation; after the second, he must re-enter Sage Mode in order to be able create additional Rasenshuriken. Once formed, the Rasenshuriken gives off a loud screeching noise. Its four points are very sharp, enough to cut through rock and disintegrate most of Pain's Human Path.

After travelling a certain distance or colliding with a target that it can't slice through, the central sphere of the Rasenshuriken detonates, producing a vortex of wind in the immediate area. Within this vortex are created countless microscopic wind-blades, so many that even the Sharingan can't count them all. The wind blades damage anything within the vortex on a cellular level, attacking the chakra circulatory system to such a degree that no amount of medical ninjutsu can heal it. Tsunade likens the damage to poison, and warns that if the damage is great enough, those effected by it won't be able to use jutsu again.

Development
When Naruto first starts using the Rasenshuriken there are two flaws in its usage: it is prone to sporadically dissipating after being formed. In order to keep it stable, Naruto must use it as a melee weapon, thrusting the Rasenshuriken into targets in the same way that he does the standard Rasengan. This in turn causes the cellular damage his targets receive to also be inflicted on whichever arm Naruto holds the Rasenshuriken with, though his arm isn't damaged quite as extensively. Nevertheless, it poses enough of a risk to him that it is classified as kinjutsu.

Naruto is able to overcome these flaws by learning senjutsu. By coating the Rasenshuriken in senjutsu-chakra, its shape is maintained after formation, meaning that he can use it as a projectile and, as a result, that he no longer needs to worry about damaging himself. When thrown, the Rasenshuriken travels very quickly, enough to cross the crater of Chibaku Tensei in under a second. Once thrown, Naruto can remotely expand the Rasenshuriken to either compensate for imprecise aim or to catch dodging targets, though its speed is great enough that this is rarely necessary. He enjoys similar benefits while using Nine-Tails Chakra Mode, where he can use his chakra arms to guide the Rasenshuriken to its target while he remains at a safe distance. Moreover, he can use these chakra arms in place of the usual shadow clones.

Naruto eventually starts making the Rasenshuriken a template for other jutsu, just as he does with the regular Rasengan. Like the Rasengan, some of the simpler modifications he makes to the Rasenshuriken are by using multiple simultaneously or making them larger (or even smaller). In place of the Rasengan he uses for the centre of the Rasenshuriken, he can use Tailed Beast Balls or Truth-Seeking Balls that will create significantly larger explosions upon detonation. He can also apply other natures to the Rasenshuriken, as he does with the Super Tailed Beast Rasenshuriken.

Trivia

 * Though the technique debuted in chapter 339, Naruto used it off-panel six chapters earlier.
 * Like the Rasengan, the Rasenshuriken's colour is depicted inconsistently in the series because Masashi Kishimoto has yet to decide upon a colour for the technique. It is most often depicted as being a bluish-white, but different promotional and supplementary material have also shown it as red or orange with no obvious pattern.
 * In Naruto Shippūden the Movie: The Will of Fire, Hiruko tries to absorb this technique, but was unable to combine the peak-levels of shape and nature transformation, like Naruto did at first. The sphere begins forming in his hand, but it becomes unstable and disperses, backfiring on him.
 * When thrown in Ultimate Ninja Storm 2 and its sequels, the Rasenshuriken would trap the target if it hit dead centre where the sphere was, pushing the target into the air and exploding.