Three years after the appearance of dungeons in the modern era, the world has adopted and started to research as well as farm the dungeons. One day the ordinary, 28-years-old researcher, Yoshimura Keigo, comes in contact with dungeons for the first time. This encounter changes his life dramatically. Curious about his newfound skill, he decides to resign from his company and live by earning money in dungeons. But will it really go as easily as he wishes? Follow this story which combines hard science fiction with fantasy in a modern world setting, and find out!