Naruto Wikia
(Updated from original post) Aside from the five basic types of nature transformation, there is also a sixth type: the Yin (陰, In), the basis of imagination and spiritual energy, used to perform Yin Release (陰遁, Inton); and the Yang (陽, Yō), the basis of vitality and physical energy, used to perform Yang Release (陽遁, Yōton).
The Yin–Yang Release (陰陽遁, Onmyōton) techniques make simultaneous use of Yin Release and Yang Release.
Yin relates to one's spiritual energy and Yang relates to one's physical energy and it's necessary to utilise both of these in order to mould chakra for ninjutsu. According to Yamato, the manipulation of Yin and Yang is the source of non-elemental techniques such as the Shadow Imitation Technique, Multi-Size Technique, medical ninjutsu, genjutsu, etc.[1]
The Sage of the Six Paths had such a mastery over the Yin–Yang Release that he used Yin to make his dreams take form, and then used Yang to make his fantasies real. He could even make them come to life. According to Madara Uchiha, the Sage's ability was called Creation of All Things (万物創造, Banbutsu Sōzō), which he employed to create the tailed beasts out of the chakra from the Ten-Tails.[2] The technique Izanagi is based on this ability. Nagato also had mastery of the Yin–Yang Release, as well as the other elemental releases by age 10
(Updated from original post) The transformation of the Yin and Yang has to do with altering the amounts of and balance between spiritual and physical energy in chakra. As explained by Shikamaru Nara, Tayuya's spirit worms were forms of spiritual energy that have small amounts of physical energy, thus they require stability and feed upon the physical energy they lack. Shikamaru also mentioned that Tayuya was the same type of ninja as he is, being able to use such kinds of "special chakra" in battle, supporting the belief that the Nara clan's shadow-based jutsu is also Yin and Yang-based.[8]
Everybody has Yin & Yang and it's their mastery of it that makes them a great ninjutsu user.
