Prolugue: I have a hero in my squad?!

Humanity is now in disarray, forced to live underground in the Ark after mechanical creatures conquered the surface which were nicknamed Raptures with the hope that one day they will be able to reconquer the surface using the Nikke.
But unknown to everyone, an event that will allow a novice commander to take possession of a weapon that embodies an ideal, the deletion of the hero of Justice.