Onmyōdō

The Onmyōdō (陰陽道, Way of Yin and Yang) is a Kekkei Genkai which is believed to be as rare as the Rinnegan itself, and appears randomly across the globe instead of being passed through genetic lineage. Currently, the only known users were Hibana Gobetsu and Arui Gobetsu. Their status as mother and son, however, was merely a coincidence.

Characteristics
The Onmyōdō is a Kekkei Genkai unique of it's kind, because it isn't positioned in the eyes or anything similar, but is directly connected to the mind and the soul. Arui has made use of this fact by developing a highly advanced and complex teleportation technique. Because the Onmyōdō generates it's on, overbearing energy, the user is prevented from using any other kind of natural transformation except for Yin and Yang. Users of the Kekkei genkai typically have a silver/gray chakra color instead of the regular blue, making it easy for sensors to detect users of the Kekkei Genkai once they know about the distinct color.

Abilities
The Kekkei Genkai generally gives the user increased strength and speed, but the actual ability is that it generates it's own, unique energy along with normal physical and spiritual energy required to form chakra. this allows the user to manipulate Yin and Yang energy in it's purest form, something normally unattainable even by users of the Rinnegan. This pure manifestation can take several forms. With Arui, it generally has the appearance of light blue flames, as seen with his Severing Void technique. With his mother Hibana, however, the energy resembled cherry blossoms.

Due the wild and normally untamable nature of the energy, the user has to form a special hand seal every time they use a jutsu, although this can be forwent by more experienced users, just like more experienced shinobi can execute normal jutsu with hand seals. Because it stands apart from other chakra natures, it doesn't really have an advantage or weakness against other elements like the "normal" ones. Instead, the Yin/Yang energy has an extreme cutting nature, being able to cut through chakra itself using the fluctuating and flowing Yin and Yang nature. Because every type of chakra has a basic yin and yang nature, the vast powers of the "pure" nature can use this varying nature in it's advantage, cutting through chakra by alternately using yin or yang nature to break it.

Inyō Mode

 * Main: Inyō Mode

As mentioned before, the Onmyōdō is a Kekkei genkai that takes place in the soul, but it is stated that it's actually "sleeping" most of the time. Through heavy concentration for an extended time period, users of Onmyōdō can "awake" it, entering a state he addresses as Inyō Mode. The energy from Onmyōdō then creeps outward at a rapid rate, creating a rejection field that negates all other kinds of energy, including chakra, kinetic energy and even time. This creates a time dilation field, thereby reducing the speed of any target that comes near him and making their efforts at attacking him useless, and thus creating sufficient enough time to counter them, aswell as granting the user incredible speed, comparable to the usage of Swift Release.

This technique also renders any chakra-based attack that comes near the user useless, as the chakra itself is forced back. Because the energy repels any other energy, users cannot use any alternate sort, such as natural or Bijū chakra. This technique also has a drawback that it repels light to some extent, rendering any users blind. Arui however, has overcome this effect by relying on his Chakra Sea Technique as a sort of alarm system, if anything disturbs his chakra near him, he can react to that. Besides this, the technique puts a severe strain on the user and cannot be used for prolonged periods, as the user himself has to use the Yin/Yang chakra to use it for other necessary energy, such as kinetic and even life force. Thus, when this technique is used to long, it will result in the user's demise. While the user's eyes are generally closed during Inyō mode due the lack of sight anyway, it's revealed that they have taken a rippled, rainbow-like pattern when opened.

Trivia

 * Onmyōdō is actually a traditional Japanese esoteric cosmology, a mixture of natural science and occultism whom is based on the Chinese philosophies of Wu Xing and Yin and yang.