After the death of the Demon King, the business of ``commercial dungeons'' became a success - Fran tries hard as a ``commercial dungeon'' designer, but fails all the time. What appeared in the hollow was a slime claiming to be the "Demon King" who had set up many dungeons!
Shougyou Dungeon To Suraimu Maou Chapter 16
Shougyou Dungeon To Suraimu Maou Chapter 17