My Army Is Bigger Than Yours

One billion humans get taken away and placed into a pocket dimension. They need to fight, cheat and kill each other to survive the harsh dimension. The winner of this wicked game will be appointed as Guardian of the Earth. Sadly, we lost. Invaders from the space manage to wipe us out. Humanity is done. However, I will not let that happen once again. I was given a second chance, and I will not let them destroy Earth like before. Come! You damn Xenos Bastard! My army is bigger than yours! Wait. It sounds as if I compare my Di–