Monster or youkai? Human! (KHR fanfic) (On-Hold)

Intro: The myth of the flames

A.N. I tried to make the story as realistic as possible but if I get something wrong please tell me.
P.S I changed between demon and monster because the Italian translation is similar to the English one and the Chinese is similar to the Japanese one.
(Es. Ita-Eng)
(Demone-demon)
(Mostro-monster)
And other....

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Thousand of years ago, when the world was peaceful and was still harmony between the creatures that lived on earth there some stories.
From ancient times there were legends about powerful flames that would only show itself to the strongest and bravest people.

The story changed from place to place but there was thing that tied them together.

In the ancient Greece there was the myth about some powerful flames that were bestowed by the god of the underworld, Hades, himself. Used to judge a person's innocence or to punish them if they were found guilty.

In the Chinese empire it was said that only the most honorable and brave hero could obtain them, the one that did everything for their empire with their dying will.

But then came the medieval era or the dark era, the time where the empires started to forget the past or destroy any evidence of it. An era where they banished the past.

The only populations that still used it were the Africans and the native Americans but then the era of the exploration came and with that the slavery and the genocide of the said populations.

Wars after wars, the humans that knew about the flames became fewer and fewer, and in the modern era they weren't even the 1% of the global population.

The story of these flames were fading away as the human who knew about them were decreasing. Those beautiful and powerful flames were almost gone in the human world but then again, who said they were the only creature that knew about the flames?

The same time as the humanity started to forget those stories, new legends started to spread all around the world. Legends about unique creatures that came from the unknown and that got powers. They were called with different names all over the world and with the names changed even their morality and their ability: - demone in Italy, monsters in America, guàiwù in China.

But the one we will talk about are the yōkai from Japan.