On the outskirts of the town within the forest reside certain low-level monsters, which adventurers often come to hunt.
A beginner adventurer was in a fight against a fiery slime, they are usually not very dangerous creatures and can be killed even more easily with some tricks but the naive adventurer was surrounded by the slime and finally swallowed by the flames and the slime.
Based on its nutrients, the slime grew a lot in size. It is not usual for a slime to beat anything. Understanding the concept that eating makes you stronger, the slime approached the nearest human town with the intention of eating everyone. And so the flames began and chaos spread.