The Onmyō Fields (陰陽田畑, Onmyō Tahata, Literally meaning: Yin-Yang Fields) also known as the "Land of Butterflies and Moths" (蝶と蛾の国, Chōtoga no Kuni) is the legendary summoning domain for the moths and butterflies summoned by Shida Yūgure. The Onmyō Fields are home to many different types of flowers and trees found nowhere else and is governed by a council. Most people and even other summoning creatures believe the Onmyō Fields to be a myth. In reality, the denizens of the fields simply prefer to keep to themselves most of the time and rarely converse with outsiders, let alone form summoning contracts. Only a few individuals throughout history have ever had contact with them, and even fewer have been allowed to visit the fields.
A few of the residents have been known to travel to the Land of Water in order to taste the "exotic delicacies" found in the chain of islands that make up the nation.
There is currently no known way to get to the Onmyō Fields on foot. In order for an individual to get there, an individual with a summoning contract has to have a butterfly or moth use the Reverse Summoning Technique. It has been noted by several individuals who live in the fields that it is possible for individuals who perform the summoning technique without contracts to be transported Onmyō Fields and that such individuals are killed unless they can convince the council otherwise.
To date there have only been three known individuals who have had the ability to summon butterflies and moths from Onmyō Fields.
- 1st Summoner
- 2nd Summoner
- Shida Yūgure
- Both sentient and non-sentient beings make up the Onmyō Fields.
- Shida Yūgure was chosen to be a summoner for rescuing an Onmyō Fields butterfly that was visiting the Land of Water from a spider's web and for growing flowers that produced delicious nectar.