Aura

Aura (オーラ) is a type of spiritual strength, assigned to each being by Kettei no Shiyakusho.

Origin
Auras have been thought to be present beside each human being from birth. Kettei no Shiyakusho, a council, had been formed to recognize this aura and officially assign it to the being. Mythologies dating back to the ancestral period depicted that a certain being, found out the existence of such aura inside each being, regardless of the nature of it, and their lethal power. Discovering the destructive powers of the auras and fearing the extinction of mankind if gotten into the wrong hands, he immediately burnt the scrolls. The mythologies that wrap the story of this "discoverer", were thought to be myths, until 5 warriors of Tenraku proved their existence, and the discoverer's theory to be correct. These 5 warriors were: The discoverers of these auras, according to the tale, had enormous knowledge of respective auras, and therefore, they mastered their aura, more than any natural being in the whole Tenraku. The discoveries led to the establishment of different clans. Each clan hence competed for power, except the one led by the Kage Ryoushu. The real plot of the Kage Ryoushu was to take control over the Tenraku, and hence, he was not at all interested in small conflicts that arose between the various clans. Roughly observed, almost each clan had beings at least of two different auras. Kuro Washi Kamon, led by the Kage Ryoushu consisted only of dark aura beings.
 * Teru Ryoushu: The head of the warriors. He discovered the existence of the light aura.
 * Kage Ryoushu: A skiled warrior, who burned in the dark flame of revenge. He discovered the existence of the dark aura.
 * Mizu Ryoushu: The most cheerful comrade. He discovered the existence of the aqua aura.
 * Kaen Ryoushu: Fiery rival of the Mizu Ryoushu. He discovered the existence of the flare aura.
 * Tsuchi Ryoushu: The eldest, in experience and wisdom. He discovered the existence of the gaia aura.

Effect
Fujisaki once described that the strength of any aura, if reached its final point, will gradually hurt the user, thereby taking his/her life. But in exchange of life, auras granted power to their wielder, making them almost invincible, when the aura strength reached its final point. Auras allows each being to create Geijutsu, a special art form, where the user uses his/her aura to create a dynamic power, powerful than a mere physical move. Auras, thus, give the user's power a further boost, only if relied upon truly. According to Teru Ryoushu, an aura gives power to its user only if the user possess a worthy reason for having that power of the aura. Aura decided a being's total strength, and his/her ability. Aura's depend on Spirit strength of the user, as they are a type of spirit power.