Earth, a world where technology develops rapidly, and world peace is achieved. This would be so, except if it weren't for...
66 million years ago, in the meteor shower that destroyed the life of the dinosaurs on Earth, various cells and DNA in these meteorites reached Earth, and evolved from there.
Monsters evolved, fairies, dragons, demons, goblins, spirits, giants appeared... They all evolved together with the species that should be the dominant one in the future: Humans.
Humans fled everywhere, they were no match for the monsters, they hid in caves, and created primitive weapons. But after generations, the population of humans was drastically reduced.
Finally, humans and spirits created a bond, and the spirits of nature created magic, mana and aura together with humans.
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Mana: It is the fuel used to cast and conjure spells. You must learn to store mana with cultivation methods. There is a limit to how much mana your mana can store. Depending on what this limit is, you will be a better or worse magician. You can conjure different spells of different elements, depending on the training you have.
Aura: It is the ability used by swordsmen. No mana is needed, the fuel is the user's own physical and mental energy. It increases your strength and speed, but it is dangerous to use if you have low stamina.