I don't remember where i read this novel, i want wait for more releases but now i can't remember the name:
I think the MC was on a trip when the change happens and then he have lucky and he get some drops of ¿water? on a mountain that helps him to ¿evolve?, ¿cultivate?
Then he become friend with a young ¿golden bull? that teach him very things, like breathing that allows he to be stronger, and information about the situation.
They also appear many powerfull monsters (like a female snake, and a old bull that became friendly with MC) and many humans evolves and mutate.
Also remember that the MC ussually eat the monsters that he kill, and he become the stronger human.
And after a battle in a forest, there are rumors of love between the snake and the bull, and the humans end up making a movie of this.
I think it's a korean novel.