A cosmic anomaly has opened interdimensional breaches on Earth, creating exotic hybrid environments called "dungeons" inhabited by deadly otherworldly creatures. Yoo Jaryong, left to fend for himself as his father's health deteriorates, secretly cultivates the superhuman potential arising from the anomaly and becomes a dungeon smuggler to pay his bills. When elite dungeon raiders discover his skills, he is given the chance to train at the alma mater of the world's heroes: Yongsa High School.