The apocalyptic outbreak begins in the most unglamorous fashion as Cain is forced to trap a newly transformed, gray-skinned student inside a bathroom stall, utilizing a broken wooden mop shaft as a crude spear to drive through the creature's skull. This terrifying initial kill triggers his first level-up notification, revealing his absurdly high mana and magic statistics alongside his primordial-rank talent, the Black Menagerie. Stepping into the blood-slicked corridors of the dormitory, Cain rescues his athletic roommate Ron, who is frozen in absolute terror despite his status as a world-class sprinter. Cain delivers a sharp, reality-restoring slap to Ron's handsome face, forcing him to shake off his shock and accept the brutal new rules of the world before equipping him with a sturdy training javelin. Together, they begin systematically clearing the dormitory floors, eventually encountering the hulking boxer Jack, who has spent his rest day painting the walls with zombie blood by beating infected students to death with his bare hands. As Cain organizes the trembling survivors and prepares to lead them out of the dormitory, the translucent interface of the Investment Harem System successfully initializes. This unique system introduces a game-changing mechanic, allowing Cain to spend gathered system points to upgrade the talents, elements, and skills of others. However, a frustrating restriction prevents Cain from directly investing in himself, dictating that only women with sufficiently high favorability toward him can become eligible targets. The system promises that any significant action, rescue, or upgrade bestowed upon these targets will return amplified investment rewards directly to Cain, turning his survival strategy toward the cultivation of a powerful female faction. With his path forward defined, Cain sets his sights on the fencing club's training hall, leaving the relative safety of the dormitory to rescue his childhood friend Elara, unaware of the massive mutated threat that blocks their path. As they step into the open campus, the distant roar of a massive mutated beast echoes from the athletic complex, signaling that the nightmare has only just begun.

Arriving at the fencing club's training hall, Cain and Ron discover a desperate battle where Elara, Cain's childhood friend, is fighting for her life against a towering, two-meter-tall Level 11 Hardened Zombie. The creature's natural bone armor easily shatters Elara's ice-infused fencing sword, leaving her wounded, bleeding, and rapidly exhausting her mana. Acting on instinct, Cain seizes Ron's training javelin, coats it in the corrosive energy of Ruin Dragon Force, and executes a flawless throw amplified by his S-rank talent, Piercing Momentum. The javelin obliterates the Hardened Zombie's skull, tearing through the reinforced concrete wall of the training hall and vanishing into the distance. This spectacular kill yields a Green Orb containing a Rare-rank Blacksteel Longsword, which Cain claims for himself despite Ron's loud protests over his lost weapon. Recognizing the value of team growth, Cain introduces a brilliant power-leveling strategy, systematically slicing the limbs off ordinary zombies and allowing the weaker survivors to deliver the finishing blows. This method boosts the group's collective level while earning Cain assistance experience. He then pulls Elara aside to deliver his first major investment, handing her the Rare-rank Frostveil Sword and a Cyan Scroll that grants her the S-rank talent, Fracture Sight. The Investment Harem System responds instantly to this massive contribution, triggering an exceptional investment return that floods Cain's body with massive stat points and grants him the SS-rank talent, Faultline Vision. This evolved talent allows Cain to perceive the structural weaknesses and movement openings of any target, elevating his combat efficiency to a terrifying degree. Before the group can celebrate their newfound strength, a massive horde of zombies begins converging on their location, forcing Cain to lead the survivors toward the university hospital in search of medical supplies and more potential allies, completely unaware of the mutated horrors lurking within the clinic. The dark corridors of the medical center whisper with the sounds of shifting limbs, waiting to test Cain's newly evolved vision to its absolute limits.

In the blood-drenched halls of the university hospital, Cain and his companion Maya execute a high-risk clearing operation, intentionally drawing hordes of infected with amplified shouts. Cain's heightened senses warn him of a Level 17 Mutated Zombie and a lethal Level 24 Blade Mantis Zombie, both of which he slays through the precise application of Ruin Dragon Force and his newly acquired Faultline Vision. The battle yields Rare-rank Windstep Boots and a Blue Orb, significantly boosting Cain's agility and perception. Reaching the barricaded fifth floor, Cain discovers a group of survivors that includes Evelyne, his childhood bully and one of the university's most beautiful students. Utilizing the excuse of a safety check to settle old scores, Cain locks Evelyne in a private room and forces her to strip entirely naked to prove she is uninfected. The humiliation quickly dissolves into a highly intimate and dominant encounter, where Cain claims her innocence and thoroughly asserts his control over her voluptuous body. Upon discovering her weak D-rank Healing Talent, Cain offers her a path to power, spending his accumulated system points to upgrade her ability into the SS-rank Saintly Restoration. This profound physical and emotional investment triggers an exceptional evaluation from the system, rewarding Cain with a duplicate Yellow Scroll. Cain immediately uses the Reward Ascension Authority to evolve his reward, unlocking the legendary Divine-rank talent, Undying God Body. This god-tier talent multiplies his physical attributes and grants him near-instantaneous regeneration, transforming him into an unkillable powerhouse. Returning to the lobby, Cain integrates the hospital survivors, including a high-level healer named Doctor Carter, and collects hundreds of metal infusion stands to serve as disposable throwing weapons. He notices the complicated, blushing glances exchanged between Evelyne, Maya, and the archery professor Irina, who accidentally witnessed their scandalous encounter behind the cafeteria, adding a layer of intense social tension to their grim survival journey. With their supplies secured, the group prepares to return to the auditorium, but a sudden world announcement echoes in their minds, changing everything.

Upon returning to the auditorium, Cain immediately humbles the arrogant Level 20 weightlifter Alex, who had attempted to extort the shelter's resources. Cain delivers a brutal, swift series of slaps that leaves Alex's face completely swollen, forcing him into submission and putting him to work sharpening the hundreds of gathered metal rods. After securing the base, Cain organizes a resource raid on the campus cafeteria, securing buses, fuel, and massive food supplies while recruiting Nathan's archery club. Recognizing that they must eventually leave the university, Cain takes an elite scouting team beyond the western gate to clear the surrounding city streets and hunt high-level targets. They soon encounter a terrifying Level 35 Ironhide Tyrant Zombie, a First Echelon entity protected by thick, metallic bone plates. Cain commands his team to focus on the surrounding mutated horde, choosing to face the Tyrant alone. Utilizing the Frostveil Sword, his SS-rank Faultline Vision, and the explosive power of Ruin Dragon Force, Cain engages in a brutal war of attrition. He systematically targets the faint weaknesses beneath the creature's armor, eventually shattering its defenses and decapitating the beast. The historic kill yields a First Echelon Core and triggers Cain's own advancement path, while allowing Nathan to successfully form a Wind Mana Core and become a First Echelon powerhouse. To prepare for this ultimate confrontation, Cain drives the team to level up, guiding Elara to complete her own advancement to become the world-ranked Glacial Sword Maiden. They lure the mutated beasts of the park into a chaotic three-way battle, allowing Cain to gather more resources, invest in new allies like the silver-haired Sonya, and forge an unstoppable path toward the capital city. As they cross the threshold of the campus gates, the true scale of the global devastation unfolds before them, revealing a ruined world where only the strongest predators will survive the coming dawn.