Onmyoudou (陰陽道 Onmyōdō?, lit. "The Way of Yin and Yang") is a traditional Japanese esoteric cosmology, a mixture of natural science and occultism. It uses Chinese philosophies, Taoism, Buddhism, and Shintoism, and evolved into the system of Onmyoudou around the late 7th century. Onmyoudou was under the control of the imperial government, and later its courtiers, the Tsuchimikado family until the middle of the 19th century, at which point it became prohibited as superstition. In Toaru Majutsu no Index, it is primarily used by Tsuchimikado Motoharu.
With its complex history and myriad influences, Onmyoudou is a spiritual path that tries of find a personal balance with the world. It deals with divination, astrology, alchemy, and exorcism. In the history of Onmyoudou it has come to use various disciplines and belief system, originally using practices prevalent in Taoism. Over the years it became refined, and incorporated various other principles, such as Feng Shui, which was used to find the balance between the natural world's power and with establishments.
At the end of its golden age, Buddhism and Shintoism began assimilating its practices.
Onmyouji were supposed to deal with the supernatural phenomena, and had powers that dealt with harmful supernatural phenomena. The Shikigami (式神 Formula God?), similar to Witches and their familiars. Shikigami are said to be invisible most of the time, but they can be made visible by banning them into small, folded and artfully crafted manikins.
In relation to the story
In Toaru Majutsu no Index, shikigamis are pieces of colored paper crafted into representing the four guardian beasts. Motoharu most famously uses shikigami as part of his Shikigami Pistol, and can destroy an entire house in a single shot.
Since Onmyoudou and the belief systems associated with it seek to have a person find balance with the world, it is only natural for it to contain teachings regarding the four elements.
Traditionally, the five elements used in Onmyoudou were fire, water, earth, metal, and wood. Onmyoudou uses "cycles", were each elements affect the other, either constructive or destructive.
In relation to the story
In Toaru Majutsu no Index, Tsuchimikado Motoharu uses the Eastern elements, and along with his expertise with Feng shui, allows him to construct magic circles for his various spells. In conjunction with Feng Shui, Motoharu is able to explain on how Kamijou Touya was able to draw the Power of the World, through the arrangements of the various charms and folkcraft he had in his home, and create a ritual location that creates the Angel Fall Grand Magic.
Motoharu also explains the similarity of Western and Eastern magic practices regarding the elements and the cardinal positions that are associated with them.
An Onmyouji (陰陽師 Onmyōji?) was a term used to refer to civil servants belonging to the Bureau of Onmyou in Ancient Japan's ritsuryo system, meaning they are professionals. However, it can be used to refer to generally anyone who uses Onmyoudou. Tsuchimikado Motoharu as a descendant of the Tsuchimikado clan is an Onmyouji.
Angel Fall Arc
- Main article: Angel Fall Arc
Introducing himself as an Onmyouji and an expert in Feng Shui, Tsuchimikado Motoharu introduces the concept of Onmyoudou in the series, and is a key player in the investigation and solution of the Angel Fall that has struck the world.
Daihasei Festival Arc
- Main article: Daihasei Festival Arc (Index)
Motoharu once again becomes a key part in the unfolding events, with his knowledge in Onmyoudou and astrology, Motoharu and Kamijou Touma were able to pinpoint the true nature of Croce di Pietro's powers.