SERA

Sera is a fictional planet in the series, with an environment similar to Earth. In an event known as E-Day, an army of Locust from underground destroyed human civilization. Subsequently, the war between humans and the Locust came to an end.The Imulsion-based weapons and bombs used in the war severely damaged the planet's environment, leading to drastic climate changes and the frequent occurrence of deadly extreme weather events known as Flare Storms. After the war, surviving humans established shelters in the ruins, but a new threat, the Swarm, began to operate on the surface.