In 3035 AD, mankind suffered a catastrophe. An unknown virus spread rapidly before people had time to panic. Those infected would die within a week. Later generations, due to its lethality, called it the death virus, also known as the D virus. Within a few years, the rest of the creatures on the earth mutated due to infection with the D virus, and they all turned into extremely aggressive "monsters."
The surviving humans gathered together and built the last and only human city-the City of Dawn in a few years.