As far as the worlds which each of them were liken in the Japanese histories, Takama-no-hara was regarded as the heaven, Ashi-hara-no-naka-tu-kuni or Izumo as the earth and Wata-tumi-no-miya as the sea. However, it is to be regretted that we do not have well ground for identifying the three countries, Na, Ku-na and Tumo, with four notable countries, Takama-no-hara, Ashi-hara-no-naka-tu-kuni, Izumo and Wata-tumi-no-miya respectively.