When portals began to connect the world with dungeons full of monsters, people with special abilities awakened. They are known as Hunters, and their task is to neutralize the dungeons before their inhabitants can invade the world. Jin-Woo Sung is one of them, but he is always referred to as a weakling by his colleagues. During a mission, he and his group stumble into a trap. His death seems inevitable, but suddenly a power awakens within him: the power of leveling up.