This jutsu is Kakashi's only original technique, though he now uses an S-ranked version known as the Lightning Blade. He created it around the time he was promoted to Jonin, and later taught it to Sasuke. This jutsu channels a large amount of chakra into the user's arm. The amount of chakra is so great that it becomes visible to the naked eye. The technique actually alters the nature of the user's chakra, effectively converting it into electricity. As a side effect of the conversion process, the large amount of chakra, and the speed at which the user moves, this technique makes a loud noise similar to many birds chirping, hence the name (if the user is not in motion, it merely makes an electric crackling sound). Once the technique is completed, the user charges forward and stabs their enemy with it. The amount of thrust combined with the large concentration of chakra allows the user to stab through almost anything; as such it is usually fatal to the enemy. This technique is classified as an assassination technique because of the speed at which it is performed, despite the loud noise it produces.
This jutsu has a major drawback, however. The speed at which the attack must be done, combined with the fact that the user must run in a straight line, causes a tunnel vision-like effect for the user. This allows their enemy to easily counter the attack, making it a potentially lethal move for the user. Though this drawback would seem to make learning the technique fairly pointless, Sasuke and Kakashi are able to avoid the drawback because of their Sharingan eyes, which take in every detail regardless of how fast the user is moving. As an additional drawback, the large amount of chakra required limits its use to a few times a day (two for Sasuke, four for Kakashi). Sasuke can manage one more than normal with the use of his cursed seal. Should the user attempt to go beyond their limit, all of their chakra will be drained and their very life force could go along with it, killing them. An additional problem, though not necessarily a debilitating one, is the fact that the large amount of chakra can also injure the user's hand if they put too much force into the attack. Sasuke does this while battling his brother, Itachi, causing some of the skin to peel from his hand and leaving it slightly smoldering after the attack was finished.
Naruto also attempted to master it, but since he lacks the Sharingan eye, this was impossible. Jiraiya used this against him to convince him to go with him to find Tsunade.
The Lightning Blade, is an enhanced form of the Chidori, with the same effects and drawbacks, but more power. It is said that Kakashi cut a lightning bolt with this technique, also speculated to be the origin of its name. Because the Chidori is already powerful on its own, the Raikiri requires much more chakra and better chakra control, which is examplfied in its appearance. The Chidori appears as simply a mass of electrical chakra in the user's hand, the Raikiri is more focused. Like the Chidori, Kakashi can use the technique four times a day, which is an incredible feat, considering the intensity and chakra requirements. Somewhere in the time-skip, Kakashi developed the ability to cast the technique on both of his hands, which has only been seen while fighting the Akatsuki member Kakuzu.
The name Raikiri seems to have derived from the Legend of the Nine Tailed Demons, where a ninja named Sarutobi (not the Third Hokage) cut a lightning bolt from the Raijuu, the Seven-Tailed Demon, with the technique Kinjutsu: Raikiri. The kinjutsu efficiently sealed the demon in a shrine
Using the power of the Cursed Seal of Heaven, Sasuke forces the use of a third Chidori. While Kakashi Hatake taught Sasuke that the Chidori was a blade that protects the bonds he made to his comrades, Sasuke warps it into a blade that severs them. The Chidori instead glows black and instead of giving off the sound of birds chirping which the Chidori was known for, the Flapping Chidori gives off the sound of many birds taking flight. While it is unranked, it appears to be many times stronger than a standard Chidori and maybe more powerful than the Lightning Blade.
A variation on a regular Chidori developed by Sasuke Uchiha during his two-and-a-half year training with Orochimaru, this jutsu allows the user to generate electrically charged chakra from his body, instead of just concentrating it in his hand. The electricity can be channeled anywhere, allowing Sasuke to enhance his attacks or defend himself. As an offensive technique, because the electricity isn't focused, it doesn't kill on contact, only paralyzes. The Current can also be sent through the ground to attack opponents from their blind spot. Sasuke can also channel the electricity through his Kusanagi sword increasing its overall strength and cutting power.
Chidori: Thunder
After delivering an elbow-blow to the enemy, Sasuke strikes them with a powerful Chidori that dicharges a lightning storm that devastates the area.
Sasuke performs a small Chidori while in mid-air.