Catacombs are labyrinths connected through gates that suddenly appeared in the world. These dungeons threw humanity into chaos but also captivated them. Only those who have awakened special skills—called Conquerors—can face the enemies that emerge from these gates. They aim to become the strongest players to save the world. The protagonist, Souta Sezaki, is the son of two players, but he failed to awaken any abilities. Making matters worse, he can “see spirits,” which causes everyone to treat him as an incompetent weirdo. One day, his childhood friend Takuto invites him into a gate, where they are attacked by the highest difficulty gate boss—the Queen Spider. As death looms, Souta finally awakens. His unique skill allows him to inherit the abilities of the deceased by resolving the regrets of wandering spirits within the Catacombs. The first spirit to appear before him is the wandering soul of his own father—the strongest flame sorcerer who died in battle. Together with his father’s spirit (manifested as a fireball), Souta challenges the Catacombs to become the strongest player!