"Labyrinth Slayer. I hereby revoke your explorer's license." "...What?" In the past, dungeons were feared as nests of monsters. However, in recent years, the resources they contain have become highly valued, leading to a coexistence and mutual prosperity between people and dungeons. As a result, Rect, the explorer known as the Labyrinth Slayer, who had destroyed countless dungeons through 'complete conquests,' was abandoned by the nobles who profited from dungeon operations and was expelled from the Explorer's Guild. After retiring, Rect, thinking that it was pointless to wallow in self-pity, took up a position as an instructor at a dungeon training school introduced by an acquaintance, while keeping his true identity hidden. However, ... "Why is the instructor so strong!?!" At first, the students looked down on Rect, who had retired at a young age, but they soon began to worship him. "The dungeons are thriving because you retired!" "Coexistence and mutual prosperity with dungeons is impossible! The upper echelons of the government don't understand!" Explorers who know the situation on the ground beg him to return to active duty, and it seems that he will not be able to live a peaceful life. Noble plots. Changing dungeons. The now free Rect occasionally shows up and influences these events. This is a story of a hero who believes his role is over and seeks a peaceful life, but unknowingly continues to have a significant impact on the world, a pseudo-sequel.