I Don't Want to Be the Savior

He never wanted to be a savior, but fate was unkind. The flame of human civilization is crumbling, but can he successfully defend it? Got the only gun in the world, but can't seem to shoot it. But when the smoke of war really rose and the once peaceful land was devastated, he asked himself for the first time in his heart: "Am I really doing the right thing?" How can he win this war when the only weapon he has is aimed at the person he least wants to harm? How to love?