Yaksha and Rakshasa

"Spell Cards
Spell Cards exist in all parallel worlds, even in worlds where all the denizens have forgotten about them.

In a certain group of fairies' world, Spell Cards have been forgotten, but they still battle in much the same way, the only difference being that battles of bullets no longer involve projectiles. Among observable parallel worlds, there is no known example of Spell Cards going out of use permanently. If it is possible, perhaps it's something only a Lost Word is capable of...

In one parallel world, the spiritual civilization of oni has built an economy based on the Spell Card Rules. By using them in the transfer of ownership rights, various forms of security deemed necessary in human material societies, like locks, keys, safes, passcodes, and passwords, become obsolete.

However, the theft of property and information using Spell Cards is also possible in this world, resulting in the development of Spell Card-based crime-prevention technology. In this way, spiritual civilizations can be seen to progress in completely different ways from any human civilization."

"The New Land of the Oni
You could say oni are a type of being born to traverse other worlds. Perhaps they came to Japan after leaving Tianzhu and traveling across China, or they may have sailed the seas to get there from some distant western land.

It's hard to imagine that an oni who's worked their way to become an administrator of Hell would abandon Hell in favor of some other place. In other words, if oni who roam from place to place did work in Hell, they surely must have been of a low rank, serving as guards or gokusotsu. Although, it's not unthinkable for a high-ranking official to be chased out of Hell for one reason or another.

The oni who appeared in the human world also tend to have a nomadic lifestyle. The famed Mount Oe oni gathered there from all over for an exquisite banquet. Then, after the Battle of Mount Oe, they went their separate ways.

Oni in a certain parallel world dream of creating a new Land of the Oni. How can the oni enjoy their day-to-day lives without any humans around?"

"Spiritual Civilizations
It's said that civilizations established by youkai are spiritual civilizations, which are supposedly the total opposite of the material civilizations (civilizations based on materialism) established by humans.

To humans, spiritual civilizations seem inconvenient and crude, but they contain an abundance of youkai-orientated features. Gensokyo is a spiritual civilization, and the Youkai Mountain society of tengu and kappa is said to have been first established by oni. It's also thought that Former Hell, the Former Capital, each region of Hell, and the Land of the Oni, which all have some relation to oni, are home to highly advanced spiritual civilizations.

Oni can use strange tools with their magic, and they're known to possess sophisticated construction techniques. It seems fair to assume these aspects of oni culture were born from their spiritual civilizations."

"Hot Spring Town
The heat of hot spring water comes from the earth. Geothermal energy is a rare energy source in that it doesn't originate from the sun.

The New Land of the Oni is found in a certain parallel world, and looks remarkably similar to the Former Capital in Former Hell. The civilization is built on a sort of geothermal energy, which they extract from the ground. What at first glance appears to be the sky is actually a pseudo-celestial sphere created by manipulating temperament. It even has a Moon. With so many different youkai living throughout, it's extremely difficult to rule over all of them. However, that's exactly what the new kishin (oni god) leaders are doing through the use of metal rods. By inserting the rods into different points across the town, they're able to activate its many giant contraptions directly. It's as if they themselves are the prime movers. When they were working in Hell as gokusotsu, they also used metal rods to maintain order, and so the kishin continue to refer to themselves as such. Even their straightforward physical attacks can be referred to as forms of kijutsu (oni magic), which is more than just simple magic."

"Paradise
The New Land of the Oni is a paradise ruled using knowledge from Hell. Some believe it can be categorized as an alternative Gensokyo.

It seems one of the worlds subjugated by the Capital belonged to a universe like the one the New Land of the Oni is in. But infinite parallel universes exist, which means there are infinite worlds that were not exploited by the Capital and continue to operate peacefully.

Such worlds are ideal safe havens... for oni, that is."