Shiranui first met Mao when they were both small children. Shiranui was undergoing the trial to prove his worth to the onmyodo master and gain acceptance into their school. In order to pass he had to wander through a complex cave system with no food, water or torch. The massive, black labyrinth had claimed many of his fellow classmates and when Shiranui had reached his limits and settled in to wait for death he saw Mao passing through the cave network without the slightest hesitation. Following the boy, Shiranui managed to pass the trial, though he was scolded by their master for doing so only through the efforts of another.
This abuse would only increase as the years passed. No matter how hard Shiranui worked he was only beaten and punished by their master. He watched as Mao and other onmyodo won praise while he toiled in obscurity, honing his skills at manipulating water. Mao gave the boy little thought after their first meeting- he was little more than another face in a crowded temple. However Shiranui was already planning his revenge. He trained a simple groundskeeper, Mokuzu, in the way of onmyoji and commanded the man to kidnap Haimaru, an act which helped to the cat into the powerful demon Byoki.
In the chaos caused by Byoki's rampage Shiranui was able to scar Mao's face. In the centuries that followed he continued to snipe at his surviving rivals from the shadows. He nearly drowned Kamon in a shipwreck at sea using his command of water and he employed Hakubi who hunted Hyakka and robbed the boy of his eye. By the 1920s he had become a powerful religious figure sought out by the rich and powerful who hoped to gain everlasting life and prosperity.
Shiranui is not without limitations however. After attacking Mao in the past he Mao, driven by the confusion of merging with Byoki, struck back at Shiranui and amputated his legs. Rather than be left a cripple Shiranui killed a water dragon and grafted its legs on to his own. Consequently he must remain in water. Shiranui has also seemingly allied himself with Yurako, a woman that appears to be Sana back from the dead.
(Source: furinkan.com)
