It had been believed that the Saeki clan was descendents of a god, Ame no Oshihi no Mikoto who had guided the way for Ninigi no Mikoto (the Prince of fertile rice-ears) when a god Ninigi no Mikoto had come down to the earth (the occasion has been called "Tenson Korin").
天孫降臨の時にニニギを先導した天忍日命（あめのおしひのみこと）を祖とし、神別氏族である。