Manga Our War that Ends the World, or Perhaps the Crusade that Starts it Anew

Empire, civilization of advanced machines and science. The Agency of Royal Possessions of Nebulas, a land considered a "state of desire." In the midst of a long, inexhaustible war between them, the boy and girl meet. Ice sorceress is revered as the most powerful: Aliceliese princes. Young fencer who is one of the greatest forces of the empire. These two meet as enemies in the war. Just as the boy is fascinated by the beauty and nobility of the girl, the girl attracts the strength and lifestyle of the boy. Collaboration is incredible, and there is not the slightest way forward, except through others. That's all.