The Nyunga Ro Chaga is the Yaku term for the host of the Water Spirit's egg. Known also as the Moribito ("guardian"), the Nyunga Ro Chaga's role is to host and protect the egg of the Water Spirit until it is born. During the events of Moribito: Guardian of the Spirit, the Water Spirit's most notable Nyunga Ro Chaga is Chagum, the Second Prince of the New Yogo Empire.
Though the Water Spirit comes from the invisible world of Nayug, it must be born in the visible world of Sagu. As such, it will choose a being from Sagu as its guardian from a supernatural being known as the La Lunga, which is known to devour the Water Spirit's eggs. While the novel implies that Water Spirit produces only one egg, thus there existing only one guardian, the anime indicates that the Water Spirit may produce many eggs with many different guardians.