Souta begins his ascent by clearing the initial chambers of the Undead Sanctuary. Armed with a rusty sword that has only two durability points left, he faces three skeleton soldiers at once, using his high agility to parry, slide, and stomp their skulls into dust. After securing the area, he uses his gamer intuition to solve the lantern puzzle, finding the hidden chamber containing the golden treasure chest. Equipping the Soul Blood Earring instantly boosts his strength, vitality, and intelligence by ten points each, giving his malnourished goblin body a massive power surge. He then proceeds to the boss room to confront the Undead Skeleton Mage, a level fifteen to twenty boss. The battle is a brutal close-quarters struggle where Souta is forced to throw away his broken sword and beat the boss to death with his bare fists, shattering its rib cage with raw physical force. This victory rewards him with nearly two thousand experience points, leveling him up to seven and netting him rare yellow-grade equipment like the Staff of Undead and the Undead's Robe. He soon moves to the ghoul dungeon, where he solves a riddle on a sealed metal door to obtain two black spellbooks, learning Mana Manipulation and Fireball. He massacres twenty-eight ghouls in a trap room, collecting their souls to feed his earring. He then confronts the Great Undead Summoner boss, dodging its ice blocks and air waves, before executing a series of consecutive stabs to destroy its head. This victory pushes him to level eight, leaving him with a massive pool of collected souls and a clear path toward his first evolution. He realizes that the local monster factions, the goblins and the kobolds, are actively fighting on the upper floor, and their war will provide him with the perfect opportunity to harvest the remaining souls he needs to trigger his first evolution.

Souta exits the sanctuary and finds himself in the middle of a massive turf war between the local goblin and kobold factions. Instead of joining his fellow goblins, Souta acts as a cold, calculating third party, observing the battle from the treetops and waiting for the perfect moment to strike. He stalks a group of twenty kobolds leaving their dungeon, identifying three evolved High Kobolds among them. Souta launches a surprise attack, throwing his sword to decapitate one High Kobold instantly, then uses consecutive fireballs to blast the others. In the ensuing chaotic melee, a spear pierces his left shoulder, but Souta ignores the pain, grabs the spear to trap his opponent, and uses Fireball directly on the kobold's face. After collecting their souls, he returns to the main battlefield where over a hundred monsters are clashing. Souta charges into the fray, mercilessly slaughtering both kobolds and goblins alike to maximize his experience points. He uses his accumulated three hundred souls to permanently boost his strength attribute, bringing it to fifty. This triggers his first evolution, transforming him into a High End Goblin. A white cocoon wraps his body, granting him a massive stat boost, the Extraordinary Body trait, and the native goblin language. He tests his new strength by invading the Kobold Leader's boss room, easily crushing the boss's guards and defeating the High Kobold leader to claim a full set of yellow-grade armor, setting his sights on the surface. To ensure he is fully prepared for the journey to the surface, he spends the next week conquering the remaining nine low-level dungeons on the upper floor, reaching level sixteen and gathering precious stones to use as currency. He knows the surface world will present new challenges, especially since he must conceal his monster identity from the humans and demi-humans who rule the cities, but his newfound physical power and high attributes give him the confidence to step through the ancient teleportation circle.

Souta arrives at Bullmar Village, a prosperous settlement near the border of the Hebrei Kingdom, where a mysterious sleeping sickness is turning the residents into crazed, red-eyed attackers at night. He accepts a rescue quest from a young boy whose sister was possessed by a strange sword and taken by a demon. Souta enters the abandoned underground base beneath the village church, fighting his way through hordes of abnormal villagers without killing them to satisfy his quest conditions. At the end of the base, he finds the boy's sister holding the Vajra Sword Saya, a dark-grade weapon that is controlling her body. The battle is extremely fierce, as the dark-grade sword boosts the girl's stats to match Souta's. Souta is forced to sacrifice his left arm to block a devastating crimson crescent slash, which explodes and leaves his arm covered in bare, bleeding flesh. Despite the injury, he uses Mud Slide and Shadow Bind to trap her feet, allowing him to disarm her and separate her from the sword. The moment the blade leaves her hand, the red woman, a physical manifestation of the sword's sentient will, emerges to fight. Souta uses his remaining mana to cast Shadow Ball, Shadow Spike, and Shadow Bind, working together with Jack and the other adventurers to finally destroy the red manifestation. He claims the Vajra Sword Saya, gaining a massive boost of two hundred points to his agility and dexterity, but he remains wary of its possession skill, knowing the sword's dark will is still lurking inside the blade. With the dark-grade weapon secured, Souta returns the unconscious girl to her brother and receives a massive reward of fifteen thousand experience points, ten free attribute points, and five skill points. He realizes that this world is far more dangerous than the game he played, as the cursed sword's influence was able to create a localized plague that almost wiped out the entire village, a scenario that never existed in the original game database.

Souta enrolls in the Ladro Institute to learn advanced magic, hiding his monster identity under the guise of a halfling. During a weekend expedition to the Desolate Woods to gather the materials for his second evolution, he rescues a green-haired girl named Cluster from a group of hooded pursuers. Souta ruthlessly tortures the survivors to discover they belong to an organization led by Curdova, who are targeting Cluster because she holds a secret from the True God's Holy Kingdom. After securing Cluster, Souta's group enters a hidden waterfall dungeon, where they defeat a level thirty Undead Cyclops boss, allowing Souta to collect the Rotten Venomous Green Apple and the level twenty undead flesh required for his evolution. However, their escape is cut off by a chaotic clash for the Mystical Light Cherry. The battle escalates when Julius and Carmilla, two powerful Commandments of the God's Will cult, arrive on the scene. Carmilla effortlessly decapitates the powerful Earth Crawler Ape with a single wave of her hand, showcasing a terrifying level of power that shocks Souta. As a massive battle erupts between the cultists and the noble reinforcement forces, Souta, Bryan, and Fred flee the area. Souta is forced to fight and kill the pursuing knight leaders Gredi and Vince, using his newly unlocked Shadow Spike and Cross Moon skills. They escape as a sealed ancient god, the Pale Horseman, is unleashed, destroying the entire Desolate Woods and forcing Souta to return to Ladros City to prepare for his next evolution. The sheer scale of destruction witnessed in the forest serves as a cold reminder of his current weakness, as the continent-level powerhouses of the God's Will cult can wipe out entire landscapes with a single spell. Souta successfully reaches level nineteen from the experience points gained during the battle, putting him just one level away from his second evolution into a Goblin Corruptor, a rare species capable of corroding living beings.