Nayug, according to the Yaku people, is a world that overlaps with Sagu, the world that most people ordinarily see. The world of Nayug is regarded as the supernatural world of the spirits of nature.
Although normally Nayug is invisible to the people in Sagu, the two interact and affect one another. Occasionally, the worlds can be seen overlapping; the magic weaver Tanda remarks that the affects of Nayug on Sagu are especially strong during the full moon, when Nayug's sun may appear in the night sky of Sagu, creating the image of a double moon.
Drinking the nectar of the shigu salua flower allows for the souls of ordinary people to see into world of Nayug while their body remains in Sagu. In rarer circumstances, humans such as the Moribito, guardian of the Water Spirit's egg, can see into Nayug without the aid of the methods of magic weavers or the nectar of the shigu salua flower.