The year 2024—the “Great Cataclysm” that took place on Halloween. Ever since, the world has turned into a hell swarming with grotesque monsters. The only ones capable of fighting back were the “Chosen Ones,” those who possess superhuman powers.K, an S-Rank individual, fought life-and-death battles against the monsters as a “dog” hired by the organization. However, in one such battle, he loses his life…But when K, who was supposed to be dead, awakens, he finds himself in the body of a baby. What's more, time has rewound to the year 2020! Somehow, he had been reincarnated 4 years before the “Great Cataclysm” occurred!To stop the impending doom, K once again confronts his destiny!