Briefly about My Eternal Reign manga:
A terrible phenomena unexpectedly wreaked havoc on the earth. The Awakeners, who had the ability to manage the Gate Cards that had appeared along with the dungeons, allowed mankind to survive this catastrophe.
Okita Hikaru, who was barely able to be considered an Awakener, was being persecuted by the Elite Awakeners at a firm that engaged in dungeon capturing during that time. After being threatened with death by a vicious dungeon monster and a heinous betrayal, Okita eventually developed a power beyond human comprehension that gave him the ability to infinitely manipulate Gate Cards. The strongest entity that defies the rules of this planet is Okita.
