The sun sets as the dusk of normality for every day humans ended with the emergence of superhumans. The beings that looked the same on the outside, and yet is capable of so much more. The first generations of superhumans exhibit the smallest amount of unnatural power, but with time, it got more and more out of control.
Then, within each of the old world's nations, war broke out between groups of superhumans and those in control. At that point, the powers have not surpassed conventional weapons in their firepower, meaning the battle fought was an even one. And with that comes far more bloodshed than either side could have anticipated for.