In the land of Terra, natural disasters of unknown causes have been occurring irregularly in many areas. Therefore, the majority of the people, in order to escape those natural disasters, came to live in mobile cities developed over the years. The Originium left behind at the site of such Catastrophes, has led to the rapid progress of civilization due to their immense energy. But it also brought something else with it — an incurable disease called Oripathy.
Arknights Animation: Prelude to Dawn, Arknights: Reimei Zensou, アークナイツ -黎明前奏-