In a world where dungeons have appeared in modern society and skilled players compete for dominance, Kanazaki En dreams of conquering the ultimate challenge—the Luluhart Dungeon. However, branded as Skill-less, he is deemed worthless and unable to even enter a dungeon.

One day, a catastrophic Dungeon Break occurs, unleashing monsters into the world. En saves a gravely injured girl, only to discover that she is the Demon King Luluhart. In gratitude, she grants him a chance to save the world—by sending him back in time.

Rewinding six years into the past, En awakens with the power of Return by Death. Armed with this ability, he sets out on a relentless journey to conquer every dungeon and rewrite the fate of the world!