A long long time ago magic and monsters were common place across the land. Then the god (or gods depending on who you ask) of our world decided to implement humans and just threw a bunch of us in all sorts of environments around the world. The results were mixed... Obviously some of us were doomed to not survive in the middle of the ocean or in a volcano. Then came those in environments that a plain human without any technology had absolutely no chance of surviving in like deserts. A bunch of other settlements died being in too close proximity to some of the more dangerous monsters. However enough were able to survive, create societies, and learn to live around or with certain monsters.
Many years occurred and human technology evolve fast with their great use of magic, and many monster breeds magically evolved to gain more human traits. Some fish monsters developed more human features which is where mermaids came from for instance. The world was changed by and adapted with the humans and their high capacity for magic considering their intellect and size. Then god decided to zap away all the monsters and magic. It was a great calamity for all the civilizations that used magic or depended on monsters... which was essentially all human civilizations. Some beasts remained but we call those animals, and god wanting to keep all traces of magic and monsters a secret kind of hid all their bones and traces... So it's not like there'd by any evidence they existed for scientists to find.
A couple thousand years later here we are at modern day. People live on several continents, we have big cities, we have fast efficient transportation with our technology, and the internet lets us communicate near instantaneously anywhere. Then for some reason the world gave out a pulse of a weird energy. Everyone felt it... something was strange in the air, but it was faint and not everyone could figure out what was different.
A few days later a bunch of Larpers made a discovery when one of their "Wizards" started wiggling their hands and fingers and spouted off random sounds of his "incantations" for fireball. Thankfully for the guy in front of the "Wizard" a fireball didn't shoot towards him, but instead a bunch of weird lights started firing from his fingers. They all stopped Larping and some thought the "Wizard" had a lot of neat effects. One of them took out their phone and asked to see if the "Wizard" could cast a "Spell" again. The "Wizard" attempted to do what he did previously, and managed to repeat the spell. There it was the first Wizard casting the first Spell since god got rid of magic. A lot of people were calling it a hoax and photoshop, but when a lot of other people had started repeating what the Wizard had done they found out that it very much wasn't a hoax. Government's ended up telling people not to try to cast random spells by making random motions and saying gibberish, but this was pretty hard to enforce unless some result happened. There were other odd occurrences such as when a politician was doing odd hand gestures while saying "Government debt is too high!" and suddenly some air alchemized into about an ounce of gold. Almost instantly gold became nearly worthless and the government debt wasn't helped in the slightest.
There was one other issue when magic came back into the world, and people started getting really interested in magic again. The people of the old world were for sure horney, and sometimes when they went out and interacted with monsters... Things happened. There would be times a random human seemingly without parents would appear. Other times a woman happened to get pregnant without having relations with a man. These humans born with monster blood would then intermingle with other humans and give birth to more humans with monster blood. When god wiped out all monsters he missed the monster blood in humans, and with the way human genes get passed down almost all humans today have some monster blood in them. Some people hypothesize that each person has a certain affinity to some of the monster blood in them, but the weird magical pulse from the Earth also seemed to reawaken the "dormant genes". Under cases of high magic or high stress or a mixture of the two people sometimes seem to metamorphize into monsters of legend, sometimes partially sometimes fully. This has led to many Wizards being very much inhuman, and that inhumanity can make a lot of people distrust them.
With the world set up let's go see the story of...