The world of Daimyo is governed by a system of celestial entities all far above mortal comprehension. With this system there is an order, beginning with the Celestial Emperor Susano-o and working down a scale of agents to the pages of the gods, often mortals given direct connection to one of the Celestial Bureaucrats. Each millennia a new ruler of the dictatorship is announced and after a series of tests brought into office in an event known as the Cosmic Progression. The ruler is dictated by the Mandate of Heaven, an over arching set of laws and regulations over 66,000 items long which must be followed directly and to the letter to achieve control of the Bureaucracy. While the rule of the Celestial Emperor is not absolute due to a system of checks and balances among different members of the Bureaucracy, the Emperor wields the most power in the heavens and is considered the highest authority regarding the Mandate of Heaven and the will of the Cosmos.
The fall of Amaterasu was actually dictated by her breach of the Mandate of Heaven and resulted in the last thousand years of darkness on earth. It is said that in the next few years during the next Cosmic Progression, Amaterasu will be lifted back upon wings of light and granted domain over the heavens once more as the new Celestial Emperor.
The Fall of Amaterasu: Long ago, before the creation of the Celestial Bureaucracy only four gods existed. The first was Fujin, God of winds, who longed for a companion and equal. From his longing was created Tsukiyomi, the moon. But his failed attempt meant that he was still alone with but the moon in the sky and the world beneath him. There in the cold dark of nothingness, the two deities strove together and created Amaterasu, goddess of the Sun, and with her birth, life spread across the world. Fujin and Tsukiyomi both loved Amaterasu deeply, as did all other beings in the world and sought to gain her favor. So it came to pass that Tsukiyomi was granted her love and became her betrothed.
His rejection enraged Fujin, and so he split the lovers, tasking Tsukiyomi to light the day in Amaterasu's absence and balance the day and night. Fujin was far mightier then Tsukiyomi and he had no choice but to agree to save the world from perpetual torment (for what can survive without night and day). Thus, each day as Amaterasu would rise, Tsukiyomi would fall and so they would forever be unable to complete their matrimony. Fujin's goal was complete and he created Susano-o to make sure the two would never meet again.
After eons of time apart, Amaterasu's heart was broken and she decided that there was no place for her within the heavens, lighting the world at her expense. She knew that she could never be with her beloved, for the Mandate of Heaven demanded there be both night and day, but she could not let this pass any longer. In desperation she fought off the mighty Fujin and crossed the world to join with her lover. As the sun and moon touched for the first time, and great star fell from the sky. The corpse of Amaterasu, once deity of light and life, crashed upon the south and warped and twisted the world as she crashed. Where she touched down nothing but death remained, and those caught in her wake became foul demons, Oni and undead abominations twisted by the death of the goddess.
For days Fujin and Tsukiyomi wept as the eclipse continued before a plan was devised. Susano-o decided that to save the world from the pending darkness they would create a new order, a bureaucracy which would protect the living from the damned and restore order to the world. Together the deities created hundreds of Kami (gods) and other spirits to fill the roles needed to sustain life in the absence of love. Thus began the first millennium of the Celestial Bureaucracy which has been in place for the last 997 years. In that time Susano-o has pushed back the tides of darkness and helped the mortals build their own kingdoms to defend themselves. Taking over as the sun he has sought to sustain the light of the world and defend against the encroachments of the dead from the realm of Amaterasu.