A Minor Inconvenience
Like their parents they were gods, but their father Onnotangu became jealous of them. Perceiving them to be a threat to him, he ate all ten of them.
Amaterasu, fearing her husband, tried helping her children by feeding Onnotangu sake with every child. By the time he reached the tenth child, Hantei, he was too drunk to realize he had eaten a rock instead.
Hantei challenged his father and cut open his belly, spilling his siblings out. Onnotangu tore a hole in the heavens and the ten children fell down to earth.
The ninth kami, whose name was since lost to time and since named Fu Leng, had fallen to Jigoku and become tainted. He later challenged his eight siblings for the Empire, leading a brutal war that culminated in the Day of Thunder.
The tenth kami died before the fall, and was forgotten by all.