In a world where dungeons appear as naturally as forests and rivers, some individuals known as Indexers venture inside to uncover knowledge, master techniques, and claim untold treasures. Rouka Ishimori is one such explorer, gifted with a unique ability to absorb and manipulate the patterns of the creatures and environments he encounters. But being an Indexer isn’t just about strength, it’s about understanding, adapting, and outsmarting  both physical and intellectual challenges. As Rouka steps into this hidden world of tests, rivalries, and ancient secrets, every dungeon becomes a puzzle, every encounter a lesson, and every choice a step toward mastery.