Can I change the course of fate?

Blurb:

A young man named Kim Zhao, swore an oath to take care of his younger brother at all costs, to protect him from all sorts of dangers. Somehow, he broke that oath when he unleashed a devastating evil whose job was to eradicate humanity. Other worldly beings started to run rampant throughout the many countries and clans of this planet, over the course of only one year more than half of humanity has been eradicated and all that's left is a measly 100 people. These people are not normal ordinary humans, these humans possess combat skills that surpass even the best military leaders. These warriors have hand to hand combat skills, gun skills, mana control and excellent swordsmanship. These enemies possess strength beyond human capabilities.