Kamui

Using the ability granted to him by his Mangekyō Sharingan, Kakashi can create a barrier sending everything within its vicinity to another dimension. He can also control the size of the barrier as seen when Pain did not notice that he warped away the nail he sent flying at him during their battle, suggesting that he did not make the barrier any larger than necessary to transport the nail to another dimension. This is significant, since the chakra consumed by this technique is proportional to the mass of the target transported. There is also said to be no way to defend against this technique. However, Tobi, who himself is a Space–Time Ninjutsu user, has told Kakashi not to bother trying to use this technique on him as it would be useless.

Kamui consumes a large amount of chakra to perform, especially in Kakashi's case, as his non-Uchiha body is predominantly not compatible with the eye; meaning it causes Kakashi more strain or fatigue than an Uchiha would experience when using the technique. Kakashi has only been shown to be able to use this technique up to three times in a given day, even when starting at full strength. When first seen, Kakashi's aim and control over the size of the barrier was imperfect. It took him two attempts to hit Deidara with the technique (still not being able to successfully take Deidara's head). Additionally, after he warped away an explosion made by Deidara, the point continued to collapse on itself even after he had transported the explosion. By the time of the invasion of Pain however, his aim improved and was even able to focus more accurately on fast-moving objects. His improvement with the technique is also seen when he manages to consecutively warp away two arrows fired by Sasuke's Susanoo (that he noted to be too fast to dodge) without immediately becoming fatigued.

Influence
Kamui is the word for a divine being in Ainu mythology, although it is almost never written with kanji in modern times. In a more general Japanese context, Kamui refers to the might and majesty of the gods, particularly the Shintō Kami.

Trivia

 * Kamui bears some resemblance to Tobi's Space–Time Migration appearance when he is warping between different dimensions. It is unknown if the two techniques are related.
 * According to the Third Databook, "If one spends a lot of time and trains one's chakra over and over again, this technique can be invoked." This might hint that other Mangekyō users can access the technique, but this is not confirmed.
 * Kakashi does not always use the technique in battle mainly due to the unpredictability of movement in battle. He does however, use it when his target's motion is defined as shown by him warping Asura Path's nail and Susanoo's arrows. This stems mainly from Kakashi's understanding of Kumai's strain on his body.