Around the fifth century, a 'Tomo' system was already established under the great king (Yamato sovereignty), in which small and medium local ruling families in the Kinai region (provinces surrounding Kyoto and Nara) and areas around it were divided into various duties of the Imperial Court hereditarily, such as Tonomori, Mohitori, Kanimori, and Kadomori.
5世紀頃には、畿内の及びその周辺の中小豪族をトノモリ（殿守）・モヒトリ（水取）・カニモリ（掃守）・カドモリ（門守）など、宮廷の各種の職務を世襲的に分掌する「トモ」として、大王(ヤマト王権)のもとに組織する体制が成立していた。