In the middle of the 21st century, in 2050, our earth is predicted to face a serious crisis because we shall run short of water by 75 percent that year. At present many scholars of authority in the world of environmental problems are formulating their theory that the way overcoming the crisis of the earth isfound in learning from the traditional ways of living of two tribes, the Celts andthe Japanese, especially the Izumo tribes. The ways of these tribes have been inherited from ancient times. In the course of history these two tribes oftensuffered severe defeats. For instance, the Celts from whom European civilizationhad its origin were driven away from the central parts of Europe to the westernfringes by the Romans and the Germans. Likewise the Izumo tribes of Japan, thetorch bearers of the native culture of Japan, represented by Oh-kuni-nushi-no-Mikoto, were compelled to hand their territory over to the Yamato Imperial Court(the Yamato-Chotei). However, these two tribes are said to hold the key to thesolutions of the question about the collapse of the earth. This paper explores thiskey and discusses the literature of Yakumo Koizumi, that is, Lafcadio Hearn, in his relationship with both the Celts and the Izumos.