Armor: Start by Obtaining the Summoner of the King of Encountering Demons

This is "Blue Star Era 3077". Human civilization has declined sharply after the emergence of "different-dimensional rifts". Countless alien monsters have poured in through the rifts. The once prosperous cities have turned into ruins. The survivors huddle in a few "safe zones" protected by high walls and energy shields, relying on remaining technology and ancient martial arts to fight against monsters.