Humanity was caught at a precipice a decade ago when the first gates—portals linked with other dimensions that harbor monsters immune to conventional weaponry—emerged around the world. Alongside the appearance of the gates, various humans were transformed into hunters and bestowed superhuman abilities. Responsible for entering the gates and clearing the dungeons within, many hunters chose to form guilds to secure their livelihoods. Sung Jin-Woo is an E-rank hunter dubbed as the weakest hunter of all mankind. While exploring a supposedly safe dungeon, he and his party encounter an unusual tunnel leading to a deeper area. Enticed by the prospect of treasure, the group presses forward, only to be confronted with horrors beyond their imagination. Miraculously, Jin-Woo survives the incident and soon finds that he now has access to an interface visible only to him. This mysterious system promises him the power he has long dreamed of—but everything comes at a price.

After a decade spent fighting monsters in the Shadow Labyrinth—a growing dark cloud of magic that threatens to engulf the world and destroy all life—mage Desir Herrman and his five companions finally face their last foe: the dragon of destruction Boromir Napolitan. Although the group of heroes manages to slay this formidable opponent, the tremendous amount of mana stored within the dragon's body is released in an unstoppable explosion that annihilates the rest of the world. However, instead of dying, Desir is sent back 10 years into the past with complete memories of events to come. He enrolls at Hebrion Academy, determined to put an end to the classist prejudice plaguing the magical world that will ultimately lead to the demise of humanity. Unfortunately, his struggle begins early on during the entrance exams; although he is ranked first of his group, Desir is assigned to the Beta Class, the default class for commoners. Now, Desir's next objective is to rally someone to his cause that he could not save in his previous life: the wind mage Romantica Eru. Then, Desir will have to show his worth to the Alpha Class with his newly formed party if he wants to ultimately save as many lives as possible.