The 国譲り was a mythological event in Japanese prehistory, related in sources such as the Kojiki and the Nihon Shoki. It relates the story of how the rulership of Japan passed from the earthly kami (kunitsukami) to the kami of Heaven (amatsukami) and their eventual descendants, the Imperial House of Japan.
Kuniumi and Kamiumi
The Kojiki and the Nihon Shoki both relate that the Japanese archipelago were created by the primordial couple Izanagi and Izanami, who also brought forth many gods into existence, three of which – Amaterasu, Tsukuyomi and Susanoo – were appointed to govern the sky (Takamagahara, the 'Plain of High Heaven'), the night, and the seas, respectively.
Susanoo, expelled by Izanagi either because he refused to perform his allotted task of ruling the sea (Kojiki) or his impetuous nature (Nihon Shoki), went to Takamagahara to see his sister. Suspected of insurrection, Susanoo protested his innocence, at which the two gods underwent a trial by pledge, giving birth to five male kami (Amaterasu's sons) and three female kami (Susanoo's daughters) when each chewed and spat out an object carried by the other (Amaterasu Susanoo's ten-span sword, Susanoo Amaterasu's magatama beads).
Declaring himself winner of the trial, Susanoo then began to wreak havoc upon Takagamahara, causing Amaterasu to hide herself in the Ama-no-Iwato, plunging heaven and earth into darkness. Though Amaterasu was eventually persuaded to come out of the cave, Susanoo was banished a second time as punishment for his misdeeds. He then came down to Ashihara-no-Nakatsukuni (the 'Central Land of Reed Plains', i.e. the earthly land of Japan), to the land of Izumo, where he slew the eight-headed serpent Yamata-no-Orochi and married Kushinada-hime. At length, Susanoo went to the underworld (Ne-no-kuni) to become its ruler.
A son (Nihon Shoki) or descendant (Kojiki) of Susanoo, Ōnamuji, married the goddess Yagami-hime of Inaba Province, earning the jealousy of his eighty brothers, who were seeking for her hand in marriage.