The End of Freedom Is Shackles and Destiny

Hundreds of years ago, enemies of mankind suddenly appeared in the world. They were huge and had super self-healing abilities. They had huge bodies and fed on humans. They were called "alien species". Facing a survival crisis, the surviving people had to flee underground and built an underground city. They built three fortresses to protect the underground city. The fortress blocked the entrance, sent a large number of soldiers to garrison, and set up two steel fortresses in the underground city. The underground people have lived peacefully in this isolated environment for nearly a hundred years. He died at the age of 12, and he and his brothers and sisters lived peacefully in the outer slums until the protagonist was 12 years old when a "giant alien" suddenly appeared and destroyed the city gate with absolutely overwhelming power, causing the ferocious "alien" to invade the outer layer of the dungeon to prey on humans. The protagonist watched many people and his sister being eaten by the "alien". So he survived and entered the second fortress with unspeakable hatred for "alien species" and the pain of losing his loved ones. Until one day, the protagonist joined the army in order to survive and avenge his loved ones. Everyone in the training camp has a strong spirit, because They all had their own goals. Three years later, after training, the "alien" suddenly attacked. Although he had seen the horror of the "alien" with his own eyes, he still bravely challenged the "alien". After surviving, he joined the expeditionary force set up to conquer the "alien", which begins the next story...