Sealless Jutsu

Sealless Jutsu (術の印無し, Jutsu no Innashi, literally "techniques without hand seals") is the act of preforming Ninjutsu and Genjutsu, including more sub-category jutsu such as Fūinjutsu, without needing to use any form of hand seals, which are otherwise a required factor in all Shinobi for the sake of preforming said techniques. It was first discovered, presumably, by Kamui Uchiha and Shōyō Kawahiru.

Overview
Kamui explained that ninjutsu is normally created through gathering the spiritual and physical energies from within the body, otherwise collectively known as chakra, and are transcripted into the desired jutsu through using hand seals as a type of structural matrix. In other terms, the energy within the Shinobi is expressed through an external matrix, which allows for the technique to take shape and substance outside of the Shinobi's body.

However, Kamui and Shōyō had come across a more advanced form of this structural matrix without needing their physical body. After their attempt to utilize the Dead Demon Consuming Seal to summon the Shinigami and learn to channel its power through their own bodies as some unique form of nintaijutsu, it had backfired and threatened to swallow them whole. Despite this, they accomplished a feat that nobody else was said to ever do, and that was to actually escape the Shinigami's being after being drawn within it. While within the death god, Kamui expressed the experience as witnessing every single possible form of death that could ever occur, even if it never had happened in human history, limited only by the collective human imagination. Again and again, the two brothers were forced to view these scenes, and in a normal case, the one sealed by the jutsu loses all command of their body and soul and are finally swallowed up. But Kamui and Shōyō were able to maintain their sense of self and escaped with their souls intact. Afterwards, they slowly began to see things in a far more broad manner. Things they did not originally understand were suddenly completely simple to grasp, and with this new-found knowledge, the ability to use this "Seal-less Jutsu" method had become second nature to them.

In the most simple terms, Sealless Jutsu allows for any form of ninjutsu or genjutsu, among other categories of jutsu, without needing hand seals to mold the chakra needed. Kamui stated that what occurs is, because the two were able to struggle against the will of the death god, the control over their own existence and soul had reached a level far beyond what even a Shinobi whom has meditated for decades on end would be unable to rival, and because of this, Kamui and Shōyō had eventually become capable of allowing their "internal persona" to act as the structural matrix to form these necessary hand seals instead of their "external persona", which would've been their own physical hands. In doing so, they can cast ninjutsu without so much as a glare or even a simple gesture, engaging in high-speed combat that would most likely overwhelm any opponent.

Notable Users

 * Shōyō Kawahiru
 * Kamui Uchiha

Behind the Scenes
The concept behind this technique was inspired after the act of using Alchemy without needing a transmutation circle found in the anime and manga series Fullmetal Alchemist.