They have a dream. One day, a dream to fly to the vast sky. Knowing how far away the sky covered by glass is. In the distant future. Humans built a mobile fortress city "Plantation" on the deserted land and sang the praises of civilization. The driver's living facility "Misttin" built there is commonly known as "Birdcage". The children live there. They know nothing about the outside world. They know nothing about the free sky. The mission they were told is to fight. The enemy is a huge life form "Calling Dragon" covered in mystery. In order to fight against the enemy they have never seen before, the children ride on robots called "FRANXX". They firmly believe that riding in it is proof of their existence. There is a boy who was once called a prodigy. Codename 016. His name is Guang. But now he has fallen to the bottom. He is an existence that is not needed by others. If he does not ride FRANXX, it is as if he does not exist. In front of such Guang, one day, a mysterious girl called 02 appeared. On her forehead, there are two gorgeous horns. "——I found it, my DARLING"