An addition-line ninjutsu that augments the killing power of a blade — like a kunai or sword — by flowing chakra into it to extend its cutting edge past the length of the physical blade-itself. The materialised chakra is shaped like a blade, cutting up everything it touches. It is also possible to alter the attack range of the weapon by adjusting the amount of chakra put into the blade. Seeing through the movements is said to be very difficult.
The density of the chakra is so high it becomes visible. It not only raises the power of the weapon, but simultaneously turns oneself into a blade as well. The chakra-enhanced blades are strong and sharp enough to cut through solid rock and iron. The technique works best with elemental chakra, especially with wind-natured chakra, which greatly increases the cutting power.
The Flying Swallow is a shōgi piece used in a large-board variant called taikyoku shōgi, which is possibly the most challenging chess-like game in existence, with over 400 pieces of more than 200 types on either side.
There may have been a mistake with this techniques classification as the second databook calls it a ninjutsu in its description, but classifies it as a taijutsu.
In the Naruto: Ultimate Ninja series, Kakashi's midair taijutsu attacks are named "Flying Swallow", "Rising Swallow" and "Falling Swallow", causing naming conflicts in that two different moves would have the same name (though a small amount of other characters have this case, though only with their normal moves). However, Asuma was not playable until Naruto: Ultimate Ninja 3, with Kakashi's "Flying Swallow" being renamed "Flying Sparrow" in the second game. However in Naruto: Ultimate Ninja 3, Asuma's technique was renamed "Flying Sparrow" instead for unknown reasons (only in the English localisations; its Japanese name is still the same) while Kakashi in both Japanese and English keeps the swallow motif for his three moves.
This also applies to Sasuke, who only in Naruto: Ultimate Ninja Storm via his past-self, has an attack named Swallow Rotating Fire (燕転火, Entenka; possibly picked up from his training with Kakashi).