Koshi is mentioned in the Nihongi as the fifth of the Great Land of Eightfold Isles to have been created by Izanami and Izanagi. This place, however, is not an island, but an amalgamation of the old Echigo, Echizen and Etchū Provinces of Japan.1
1. Aston. W.G. (1896) “Nihongi Volume 1: Chronicles of Japan from the Earliest Times to AD697”. Tuttle Publishing.
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