In the fourth season of Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka, the valiant adventurer Bell Cranel continues his journey of growth. Despite his advancements, the Hestia Familia faces a challenging path to rival the other powerful Familias in Orario. Just as Bell prepares for his next quest, a shocking murder shakes the adventurer community. Accusations fall upon one of Bell's closest companions, prompting him and his allies to embark on a mission to prove their innocence and unveil a sinister conspiracy lurking in the shadows of the dungeon.