He was a friend and supporter of the Prince Naka no Ōe, later Emperor Tenji. Kamatari was the head of the "Jingi no Haku", or Shinto ritualists; as such, he was one of the chief opponents of the increasing power and prevalence of Buddhism in the court, and in the nation. As a result, in 645, Prince Naka no Ōe and Kamatari made a coup d'état in the court. They slew Soga no Iruka who had a strong influence over Empress Kōgyoku; thereafter, Iruka's father, Soga no Emishi, committed suicide.