Onmyoudou (陰陽道 Onmyōdō?), also known as Shamanism, is a style of eastern magic that combines concepts and aspects of Taoism, Buddhism, Shintoism and Kuji which originated from Japan. Practitioners of it are called Onmyouji (陰陽師 Onmyōji?).
It flourished heavily during the Heian Period to the point where it once held great influence in the Imperial Courts, but the tradition eventually waned and nearly died out. However that changed between time of the Meiji Restoration and World War II, where at that point Japan was desperate to become a world power. To that end it reopened sorcery once again and allowed it to be integrated into the military with the prosperity of the country's future in mind, thus the era of "Restoration of Magic" began with Tsuchimikado Clan being the central figures of its new movement.
Around the period of World War II, Yakou Tsuchimikado had collected all of Japan's magical traditions and refined them into completely new all encompassing style of magic, stripping them of the religious borders that held them separate, called the Imperial-Style which lead to major victories and huge gain of political power for Japan in the war. This system was later further refined and simplified into what is now known as Common-Style giving birth to the modern Onmyoudo. Now magic continues to thrive and has now become a institutionalized aspect of society with multiple applications in various fields such as medicine, and technology thanks to the efforts and achievements of Yakou after World War II.
Imperial-Style: A revolutionary magic system created by Yakou after gathering, breaking down, rebuilding and refining old Onmyoudo at the behest of military. Being the culmination of all of Japan's magical techniques, and knowledge it is highest form of magic in the nation's history. Because it was created for military and political purposes (and not civilian use) it removed many of religious and abstract elements of old Onmyoudo and focused on practicability.