The Mayfly Dynasty

In a world corrupted by dark demons, humanity began developing supernatural abilities to fight off demonic invasions. But some people chose to join forces with the dark demons, sparking endless conflicts between the various factions. By chance, the protagonist and a friend encounter a dark demon. On the brink of life and death, the protagonist is cursed and gains a supernatural ability, then gets sent to a supernatural academy. He draws a spot in an exchange student program and enters a rival academy, where he gradually discovers the dark side of the Supernatural Ability Association. A defeated nation rises once more, and a new war begins...