Rokushiki/Soru

With leg strength explosive enough to seemingly cause one's body to "disappear"...

Soru is one of the six techniques of "Rokushiki".

Overview
The Soru allows the users to move at extremely high speeds in order to avoid attacks, as well as to attack at higher speeds and with greater power. It was revealed that the principle of this move was to kick off the ground at least ten times in the blink of an eye. Coby was seen being able to use this move during his friendly fight with Luffy after the Enies Lobby arc and during the Marineford Arc. As Nero lacked the complete training, his Soru is actually more of a swift run instead of the vanishing speed seen from other Soru users.

Monkey D. Luffy gains access to the Soru technique when he utilizes his Gear Second mode, which pumps up his metabolism and allows him to move at disappearing speeds, which surpasses even Blueno's.

Another thing that should be noted of this particular skill is that Kuro's "Shakushi" travels at roughly the same speed as CP9's Soru ability. The difference is that when Kuro uses that technique, he cannot see what he is attacking, or how far he is going, whereas CP9 have mastered this ability and therefore can. The fact that other people, outside of CP9 membership have exhibited being able to imitate the skill (either by copying the move directly or developed their own version of it) suggests that Soru might be the most fundamental of Rokushiki. This is supported by the fact that Coby uses (and masters) Soru, though he has not shown the ability to use any other Rokushiki techniques.

Variations

 * Kamisori (剃刀): Used by Lucci. A combination of Geppo and Soru, where Lucci uses Soru in a zigzag motion in midair, allowing extremely fast movements in three dimensions, other CP9 agents have also shown to use this technique or a similar one allowing them to move through the air at great speed. In the Pirate Warriors series, Lucci can use Kamisori to cut through enemies while utilizing its high-speed movements, and he can use the attack in his human form in the third Pirate Warriors game (while ending it with a smashing dive). In the Viz Manga, this is called Razor. In One Piece: Burning Blood, it acts as Lucci's special movement in his beast form.
 * Soru "Tekkai Dama" (剃「鉄塊玉」): Used by Fukuro. In this attack, Fukuro spins his body at great speeds towards his opponent using Soru, then uses Tekkai to harden his spherical body. In the Viz Manga, this is called Shave Iron Ball.
 * Cho Sokuten Tekkai Dama (超側転　鉄塊玉): A variation on the above technique used by Fukuro wherein he combines his usual Tekkai Dama movements with Geppo to use it in midair. In the Viz Manga, this is called Super Cartwheel Iron Ball.

Trivia

 * While Soru grants the users the ability to move at disappearing speeds, there are other people capable of achieving such a feat (discounting Devil Fruit users such as Enel and Borsalino) without the technique (or at least calling out the technique's name); the known people are Laffitte, Riku Dold III, Dellinger, Hakuba, Minotaurus, Heaby, and Musshuru.
 * The anime expands the capabilities on those who abuse Energy Steroids, gaining speed akin to Soru, namely the captain and officers of the New Fishman Pirates.