The Beginning
The concept of a beginning is a curious thing, but our tale must start somewhere. From the myriad gods which inhabit this realm, two legendary beings emerged; these were known as Izanagi and Izanami. Together, these beings descended from the heavens and thrust a great jeweled spear into the vast ocean creating the eight islands of the Japanese archipelago - the first land. Izanagi and Izanami sought to populate the new land, and imbue it with the powers of existence. From their intercourse were formed the first kami, entities which lie somewhere in the gray area between gods and spirits. Some benevolent and some wicked, these kami permeated the natural world to create and hold dominion over a great many elements, concepts and qualities.
Death and Rebirth
Being mortally injured from birthing the kami of the fire element, Izanami passed away to the underworld in the land of Yomi. Desperately seeking to reunite with his partner, Izanagi risked venturing into the land of the dead in search of her. When Izanagi found Izanami and looked upon her, he saw that her flesh was rotting and maggot-ridden. Horrified, Izanagi fled from Yomi and sealed the entrance behind him with a great boulder, forever separating the world of the living from the world of the dead. Disgusted by his close contact with the rotting body if Izanami, Izanagi plunged himself deep into the ocean so that he might be purified of the experience. As a result of this purification, many new kami were born. Among these was Amaterasu.
Assigning an Emperor
Amaterasu was the sun goddess, and she was also tasked with dominion over the land; a giver of life. Amaterasu had many children and grandchildren, and one day came to the realization that the great nation of Japan should be ruled by an emperor. She cast forth one grandchild by the name of Ninigi, whose son - Amaterasu's great grandson - would be Jimmu Tenno, the first emperor of Japan. Henceforth, Jimmu's bloodline would be considered that of divinity and his family would forever rule over the land.
The Eight Kami
Jimmu Tenno would, over time, be diluted and detached from his kami essence as a result of his exposure to humanity and his indulgence in worldly pleasures. Jimmu would remain forever ignorant of the eight other kami sent forth by his great grandmother, Amaterasu, and their divine bloodlines which were to be tasked with dominion over eight elements of the world. These kami were created by Amaterasu's hand from worldly material; they would assume a human-like form and live in relative solitude, their descendants taking surnames after the names given to them by Amaterasu herself:
Seikatsu, created from a stream of sand allowed to slip through Amaterasu's fingers; he and his lineage are charged with overseeing the continuity of daily life; the regular cycles of sun and moon (Amaterasu and Tsukuyomi), the coming and going of seasons, and new life and new death. @
Howaitora, created with frozen snow from the peak of the highest mountain; he and his lineage are charged with guarding all things at a high altitude; the climbing of steep, icy mountains made a very perilous endeavor, and the clouds always kept pure and high - far from the grasp of humanity. @Stylishninja
Enzan, created from the most beautiful flower in the world which was found and plucked by Amaterasu; he and his lineage responsible for maintaining the balance and harmony of the natural world, ensuring that all things in nature interact peacefully and remain beautiful. @Crosswise
Shousetsu, created with an urn of ocean water which Amaterasu foolishly took from her brother, Susanoo; intended to rule over the cycle of evaporation and condensation of water. However, Susanoo being a kami of storms and destruction, the water which was used to create Shousetsu was of a dangerous nature. This kami forsook his original task and defeated Konpira - the kami of safety at sea - in combat; he and his lineage now hold dominion over the oceans, permitting safe travel and inflicting turmoil at their discretion. @Sipher
Tetsumei, created from a fragment of Ninigi's broken mirror; he and his lineage are tasked with the structuring and distribution of wisdom with relation to universal truth and rationality, allowing enlightenment to those deemed worthy and withholding it from those who are not. @Mr.Yagura
Donsu, created from the dreams stolen from other kami; he and his lineage maintain the boundary between reality and the world of dreams, blocking off from the minds of humans and other kami those which are dangerous or forbidden, and permitting them only dreams which the Donsu deem important. @Gary Oak
Raishuu, created from the blood of Amaterasu herself, which she spilled during her time of solitude and depression; he and his lineage are charged with dominion over all human conflicts; the Raishuu determine the outcome of wars, and are responsible for inflicting and relieving human suffering. @Undo
Minamiyori, created from the deep, black roots of a weeping pagoda tree; he and his lineage are charged with dominion over thick forested areas as well as the darkness and shadow which inhabit them. All things which happen in concealment are attentively presided over by the Minamiyori. @Southend_boi