Synopsis

A newly discovered dungeon, accessible only to a single challenger who cannot re-enter after a failed attempt, presents a unique problem for the KBI. After two SS-rank heroes fail, they call on the protagonist, who initially came for a private dungeon. He agrees to conquer the difficult dungeon, characterized by traps, monster resistances, and darkness, in exchange for monopolized access to a private A-rank dungeon. He is briefed on the dungeon's hazards before venturing in alone.