On his way to Mount Katsuragi (a mountain on the border between present day Osaka and Nara Prefectures), while passing Kasuga Field in Yamato Province (Nara Pref.), a mountain ascetic (waki) from Mount Haguro (a mountain near present day Tsuruoka City, Yamagata Pref.) encounters an elderly field warden (shite in act one).
The ascetic asks about the name of the pond in the middle of Kasuga Field. The old man replies that since the field wardens look at their reflections in the pond, it is rightfully called Warden's Mirror. However, the true Warden's Mirror is in fact the mirror of a Demon God that lived here in ancient times.
The ascetic remembers the old poem: "The Warden's Mirror that revealed the hawk's reflection...", and the old man says that the Warden's Mirror from the poem is this very pond - the Emperor had lost sight of his hawk while hunting and had seen its reflection in the pond. The ascetic inquires further about the whereabouts of the Warden's Mirror that belonged to the Demon God. The old warden tells him to look in the reflective water of the pond, and then mysteriously disappears into an old mound.
Confused, the ascetic asks a local man (ai) about the Warden's Mirror and the recent encounter. The local is certain that the old man had in fact been the Demon God himself.
Curious to see the actual mirror, the ascetic prays in front of the old mound, hoping for the Demon God to appear again. Suddenly, the Demon God (shite in act two) appears from inside the mound, holding a mirror in his hand. The ascetic rubs his prayer beads and fervently prays. Impressed with the pure-hearted ascetic uttering his devil-quelling prayers, the Demon God lifts the mirror and shows him the vastness of the universe, the bounds of Hell and the diversity of the other worlds. Finally, the Demon God returns to the bottom of Buddhist Hell.
"Nomori" means "warden or caretaker of the fields" in Japanese. In ancient times, such wardens were responsible for the fields being in pristine condition, so that the aristocrats could go on outings to pick young sprouts during the spring. A thorough knowledge of the fields was required. They would even serve as guides to the Emperor during his hawk-hunting trips.
"Nomori" is a demon type of play (also referred to as ‘oni-noh’) created by Zeami. In the first act, the old man appears as the shite and tells the story of the lost hawk that was found thanks to its reflection in a pond. In the second act, the old warden appears in the form of a Demon God - a powerful and energetic role.
Although the role is of a Demon God, he is not an evil demon who ought to be vanquished, but a good one, sworn to set straight a world full of evil. His acting while holding the mirror is particularly fascinating.
An essential theme in this play is the concept of the Warden's Mirror. In the anthology "Kokin Wakashū", there is a love poem that reads: "The Warden's Mirror that revealed the hawk's reflection - oh, how I long to look inside it. Does he love me or not - only then shall I be sure".
There is a legend related to "The Warden's Mirror that revealed the hawk's reflection". While on a hunting trip, the Emperor lost sight of his hunting hawk. However, the field warden looked at the surface of a nearby pond and saw the hawk's reflection in it. This is how it was found.
The Demon God appears holding the actual Warden's Mirror. Here it is depicted as a magical device that is able to not only find any lost object, but also to reflect the landscapes of various worlds.