Myths and Legends of Japan

We are told that in the very beginning, "Heaven and Earth were not yet separated, and the In and Yo not yet divided." This reminds us of other cosmogony stories. The In and Yo, corresponding to the Chinese Yang and Yin, were the male and female principles. It was more convenient for the old Japanese writers to imagine them coming into creation not very remote from their manner of birth. In Polynesian mythology, we find pretty much the same conception, where Rangi and Papa represented Heaven and Earth, and further parallels may be found in Egyptian and other cosmogony stories.
We find the male and female principles taking a prominent, and after all, very rational, place in nearly all.