It has been over ten years since Gates, dimensional portals connecting different worlds to the present world, began to appear across the globe. The battle between humans—who have awakened with superhuman powers and are known as Hunters—and the monsters that inhabit the dungeons inside these Gates, rages on without end.
Typically, once a Hunter awakens, their abilities do not grow, and their rank remains fixed. However, Shun Mizushino, a low-rank Hunter who was once called humanity's weakest weapon, gains the ability to level up during a raid in a dual dungeon, a power that no one else possesses. As he continues to fight, his abilities grow stronger.
After completing a class change quest, Shun obtains the title of Shadow Lord, a profession that allows him to command shadow soldiers. With his newfound strength, he embarks on a new battle in search of the "God's Water of Life", a material that could cure his sick mother.