Episode 4 of Solo Leveling picks up right where the previous episode concluded, depicting the Steel-Fanged Lycan lunging at Sung with ferocious intent. Quick on his feet, Sung narrowly dodges the attack and retaliates with a powerful punch, setting the stage for an intense scuffle. Amidst the fray, Sung's concern for his safety grows, prompting him to summon the inventory menu of his log and wield a magical sword. With a decisive strike, he vanquishes the Lycan.
Scarcely catching his breath, Sung finds himself confronted by two more Lycans as he struggles to extract his sword from the earth. Through sheer determination, he manages to free the blade, which promptly claims the life of another Lycan. The third Lycan, recognizing the odds against it, flees, allowing Sung a moment of respite. Scanning his log's menu, he notices a surge in his level and stats, a testament to the real-world combat he has endured.
Curiosity piqued, Sung approaches one of the fallen Lycans in search of an essence stone. To his disappointment, the beast carries none, but instead, bestows upon him a Lycan fang as a grim reward. Realization dawns upon Sung that this log's dungeon and its magical inhabitants deviate from the norms of typical gates. Suddenly, a store materializes, tantalizingly out of Sung's reach due to his current level constraint.
Undeterred, Sung sells the Lycan fang for a modest 20 gold pieces, wondering aloud if this sum constitutes wealth and contemplating the enigmatic rules governing this instance dungeon. His musings are interrupted by the sudden appearance of numerous Lycans, forcing Sung to engage in battle with all his might.
With each Lycan he slays, a cascade of level-up notifications floods his vision, culminating in Sung earning the prestigious title of Wolf Assassin. Having vanquished all his foes, Sung realizes that his sword is nearing its breaking point. The Wolf Assassin title log reappears, this time announcing that he has earned a multitude of items, including a teleportation stone. Unhesitatingly, Sung chooses to delve deeper into the "instance dungeon."
Meanwhile, Joohee receives a phone call from the same individual who contacted her in episode three. The caller informs her of a dungeon breach at the very mission she had declined earlier. Emphasizing the desperate need for healers and with Sung's well-being in mind, Joohee reluctantly accepts the mission.
Meanwhile, Sung finds himself engaged in the slaughter of magical beasts, advancing through the treacherous instance dungeon. He takes note of the telltale hues of the monsters' titles, which serve as indicators of their strength and how this coloration shifts with his evolving level. Embarking on a perilous journey, Sung anticipates encountering a formidable magic beast that will push him to his limits.
As he wanders through this hazardous terrain, the anticipated beast strikes, shattering Sung's sword in a flash of combat. Emerging before him, the beast reveals its name glowing in an ominous orange, signifying an equitable match. Identifying this serpentine creature, or Kasaka, as the dungeon's pinnacle challenge, Sung braces for battle despite his uncertainty about piercing its seemingly impervious scales.
In the throes of his confrontation with Kasaka, Sung's mind wanders, contemplating themes of bravery, vulnerability, and might drawn from his extensive experiences as both a hunter and a citizen. Drawing upon unyielding resolve and the haunting memory of the God statue, Sung employs his might to choke the life from Kasaka.
Suddenly, multiple log entries flood his vision, announcing his substantial level advancement, a testament to his victory. Additionally, Sung acquires a dagger crafted from Kasaka's fangs and a Venom Gland, though he suggests storing the latter due to its intimidating aura.
The log's conclusion whisks Sung back to Earth, where he chances upon a soldier who leads him to a dire occurrence. He learns of a dungeon breach and utilizes his heightened perception to pinpoint the boss's location. Arriving at the scene, Sung observes a group of hunters and healers struggling against the dungeon-breaking beast. From afar, he assesses the battle, identifying the flaws that have hindered the party's progress.
Among the combatants, Sung notices Joohee, still reeling from the God Statue incident. Recognizing the boss as weaker than himself, Sung hurls his shattered sword, shattering its defenses and enabling the party to claim victory. One party member spots Sung's dagger and inquires about its origin from a nearby mercenary, but Sung flees before an introduction can be made.
Elsewhere, Sung marvels at his ability to pierce the boss's defenses with mere fragments of his sword. The episode concludes with Joohee pondering whether Sung was the mysterious sword-thrower.
