Wikipedia
Ōmononushi is a kami in the Japanese Shinto tradition. He is associated with Mount Miwa and is worshipped at the Ōmiwa shrine there.
During the reign of Emperor Sujin (around 97-30 BCE), a plague affected the country. After Ōmononushi's descendant, Ōtataneko, petitioned the kami, the Emperor had a dream in which Ōmononushi appeared to him and claimed responsibility for the plague, announcing that it would not stop until an appropriate priesthood was set up on Mount Miwa. When the Emperor created such a priesthood, the plague ceased. Ōmononushi was worshipped as a nature spirit who provided good weather and bountiful harvests, and was strongly associated with snakes.
At least two legends tell of Ōmononushi fathering children with human women. On one occasion he transformed himself into an arrow in order to impregnate a girl named Seyadatarahime, whilst on another occasion he used the form of a snake to have a son with the maiden Ikutamayorihime. In the Kojiki he is recognised as the ancestor of Himetataraisuzu-hime (Isukeyorihime), the spouse of Emperor Jimmu.