Izure Shinwa no Ragnarok

Seven deities once waged war on Earth, causing catastrophic destruction. A decade later, a boy named Raika lost his younger sister to one of these gods during the conflict. Now, he resides at an Academy located on an artificial island in the ocean. At night, known as after-school time, a proxy war among the gods takes place, using individuals compatible with divine power to determine the world's ultimate authority. On his first night there, Raika is attacked by the Norse deity Brynhildr. Confronted with death, he gains a godly power of vengeance—the power of absolute domination—through the devil eye of Balor. With this new ability, Raika seeks to reclaim the world from the gods' grasp.