The Earth's Chosen Savior (Novel)

When the universe decides to destroy Earth in forty-two days, the planet responds by distributing its essence to all its creatures, both human and animal. They must use this essence to defeat monsters invading through gateways from an alien world. The more essence one possesses, the more powerful one becomes. Jeong-u Park, a game studio employee, discovers he has been chosen by Earth as one of its saviors, but he only receives a small amount of essence at first.
Obsessed with saving Earth, he realizes that the only way to collect enough essence to close all the gateways is to kill other people. As Earth hurtles toward its end, Jeong-u faces more and more dreadful monsters pouring out of the gateways―and more people he must kill in order to defeat them.

Original Novel
Official English