Mark's first real challenge in this new world arrives not as a direct threat, but as a gamble. Deep within the dungeon, he finds a mass of rotting flesh and fused bones—a sleeping monster. But among the scattered corpses, one stands out: Elyndra Ashford, a legendary SSS-rank Holy Knight, dead by her own poisoned hand. Mark, recognizing her legendary gear and rank, sees a terrible, morally questionable opportunity. His only skill, Wake Up, can partially revive a corpse without consciousness or free will. He gambles that an SSS-rank corpse will retain her power. The gamble pays off spectacularly. Elyndra rises with max stats and absolute loyalty. Mark, now Level 2, unlocks "Consciousness Modification," a skill allowing permanent alteration of an undead's memories and personality. He crosses a clear ethical line, programming Elyndra to be hopelessly, obsessively in love with him, his "master" who saved her from death. The monster wakes, but Elyndra, a walking weapon of mass destruction, dispatches it in seconds, her golden-light sword effortlessly slicing through its form. Mark, now Level 3, realizes the terrifying potential of his new cheat. He's no longer just a mediocre man; he's a necromancer with a legendary, devoted warrior at his command, ready to face the unknown world outside the dungeon.

Emerging from the dungeon, Mark learns the harsh truth: necromancers are social pariahs, viewed with disdain. Elyndra, his obsessively loyal companion, accepts this without question, her devotion unwavering. Mark, still thinking with a video game mindset, registers as a Rank F necromancer in the town of Millbrook, drawing immediate suspicion but dismissed as harmless. He begins a double life, using Elyndra to clear dungeons (Rank D Shadowwolf Cave, then Rank C Crypt of the Fallen), rapidly gaining experience and gold while he hangs back. His progress is noticed; adventurers question how an F-rank necromancer clears high-level dungeons solo. Mark lies, claiming he "repurposes monster corpses," a partial truth. The City Council summons him, and he spins another lie, stating his reanimated monsters decompose after each dungeon. The Council, though wary, accepts his explanation for now, warning him against using necromancy on humans and promising to watch him closely. Realizing his deceit is unsustainable in Millbrook, Mark decides they must leave, seeking anonymity in a larger city, pushing deeper into the shadows of this new world.

On the road to Thornhaven, Mark's path takes an unexpected turn. He uses his newly unlocked "Aura of Death" skill to scare off bandits harassing a young girl named Lily, an act of unexpected heroism for him. In Thornhaven, the guild receptionist, an observant elf, notes his "unusual" dungeon clears and necromancer class, adding to his unease. Seeking a safe base and faster leveling, Mark decides to tackle the S-rank Pit of the Forgotten, a notorious "hero's graveyard." Inside, his aura of undeath surprisingly makes the dungeon monsters ignore him. There, he discovers another powerful corpse: Yuki, an SSS-rank assassin, dead from a seemingly mundane insect bite. Mark, seeing another opportunity, revives her. This time, he uses Consciousness Modification more subtly, making Yuki loyal, obedient, and silent, but not obsessively in love, learning from his past excess with Elyndra. However, Elyndra immediately senses Yuki's presence and displays overt jealousy, creating a palpable tension between the two powerful undead women. Mark now has two SSS-rank warriors, but the emotional cost of his creations is already surfacing.

Aria Lightwood, Lily's SSS-rank healer sister, approaches Mark under false pretenses, expressing gratitude for saving Lily. Mark, despite Ely and Yuki's warnings of danger, agrees to meet her. Aria leads him to an abandoned building, revealing it as a trap. She despises necromancers and had used Lily and hired bandits as bait to lure him, aiming to kill him herself after her ambush team failed. Ely and Yuki materialize, saving Mark and holding Aria at blade-point. Aria, horrified to recognize the legendary heroes she called "abominations," brands Mark a "monster" for defiling them. In a cold rage, Mark chokes Aria to death with his bare hands, his first direct kill. He feels only emptiness. Immediately, he decides to revive Aria, not out of kindness, but "necessity," for her SSS-rank support skills. This time, he goes full throttle with Consciousness Modification, making her submissive, masochistic, perverted, and shamelessly devoted. Aria revives, ecstatically grateful for her "Master" killing her. Mark unlocks "Shared Life Essence," a skill that equalizes party stats to the strongest member. He then defeats the S-rank dungeon boss, the Abyss Devourer, and due to his necromancer affinity, subjugates it as his pet, Vorax, and becomes the dungeon's owner. Mark now controls an S-rank fortress, but at the cost of his humanity and a deeply disturbing addition to his harem.

Mark, now a Dungeon Lord, faces a new problem: he can't gain experience from monsters killed in his own dungeon. He needs to leave his new fortress to level up. His next target: the Demon Lord's Dungeon, which he believes is an abandoned, high-level grinding spot. He takes Yuki and a newly revived vampire, Rose, with him. Rose, immediately perceptive, questions Mark's naive plan to passively clear such a formidable dungeon. Inside, they find no monsters at the entrance, but soon encounter a powerful group of adventurers, led by an SSS-rank cleric named Alice Valthyra, already fighting the dungeon's inhabitants. Mark witnesses Alice's incredible self-enhancement miracles and brute strength firsthand. Realizing the immense power of this dungeon and the opportunity, Mark makes a swift, ruthless decision: he orders Vorax to finish off the unconscious, defeated adventurers, then revives Alice and her companions. Alice, an SSS-rank Cleric, becomes his newest subordinate, specialized in pushing her body to superhuman limits. Rose, though initially against the idea, acknowledges Mark's cold, pragmatic decision-making. Mark almost died underestimating this dungeon, a stark reminder of the dangers of this world.

Deep within the Demon Lord's Dungeon, a mysterious voice calls Mark by his true name, "Mark," unsettling him deeply, as no one in this world knows it. Emerging from the dungeon, the group is confronted by a powerful demoness who immediately recognizes Mark as a "reincarnated one." Mark, panicked that his deepest secret is exposed, orders Vorax to attack, but the slime is overwhelmed by the demoness's immense power. The demoness effortlessly defeats Ely, Yuki, Aria, and Alice, leaving them battered and unconscious. Rose, revealing a hidden teleportation spell, can only guarantee a safe escape for herself and Mark. Faced with an impossible choice, Mark orders Rose to somehow save everyone, even if it strains the spell. They barely escape, landing in a forest clearing, defeated and exhausted. Later, Rose confirms she knew he was reincarnated, having sensed it in his "aura" during their intimate moments. Mark is left reeling from the devastating defeat and the terrifying exposure of his secret, his plans shattered and his vulnerability laid bare.

After their crushing defeat, Mark and his battered group recuperate in a forest camp. Mark himself falls ill with a cold, leaving him vulnerable and frustrated. The internal tensions of his growing "harem" surface as Rose and Alice clash, and Ely and Aria bicker. Mark, despite his sickness, intervenes, using his authority to establish order and remind them of their shared purpose. During his recovery, Mark shares intimate moments with Rose and Alice, deepening their devotion and his own complex feelings. He finally gathers his entire group (Ely, Yuki, Aria, Rose, Alice, and Alice's revived companions) and reveals his reincarnation, explaining how the demoness knew. He addresses the internal conflicts head-on, promising not to abandon them and establishing clear rules for their cooperation. Meanwhile, Captain Hod, a formidable inquisitor, and her team are hot on their trail. They discover the devastated semi-human camp, a clear sign of Mark's group's power, and realize a major hunt is underway. Mark, still recovering but with his fever broken, finds himself at a crucial juncture: his group is larger, more powerful, and united by shared secrets and devotion, but a relentless, organized enemy is closing in, forcing them to move and plan their next steps carefully.