One year ago, our world shattered by monstrous invasions, the population plummets from 8 billion to 3 billion, leaving deep scars and a desperate struggle for survival. Amidst the chaos, Kim Yuri, a young college graduate, finds himself the unlikely guardian of his 4-year-old niece, Jimin, after a tragic event rips apart his family, leaving him with a profound sense of loss and responsibility. When the Korean government resorts to forced recruitment to clear deadly dungeons managed by enigmatic elves, Yuri - an E-ranked nobody with no combat skills - is thrust into the fray, joining forces with two elite S-rank tankers who are renowned for their bravery and skill.
As Yuri navigates this treacherous new world,he become reason for korea to lose one more S ranker, his ineptitude sparks disaster, earning him the scorn of his peers and the nation. But just as all hope seems lost, a mysterious 7-year-old child claiming to be a prince appears, foretelling doom unless Yuri can conquer the dungeons and reset the apocalypse's countdown. With humanity's fate hanging precariously in the balance, Yuri's unassuming journey as an "average" hero begins - can he overcome his limitations, rise to the challenge, and save humanity, or will the world succumb to darkness and destruction?