"Isekai Meikyū de Harem o" is a manga series that blends elements of fantasy, adventure, and harem genres. The protagonist, a young man dissatisfied with his mundane life, finds himself transported to a fantastical world after interacting with a mysterious website. This new world is structured around a labyrinthine dungeon system, where adventurers must navigate treacherous environments, battle monsters, and acquire skills and items to survive and grow stronger.

Upon arrival, the protagonist gains a unique ability called "Gift," which allows him to allocate skill points and customize his abilities. This power becomes crucial as he delves into the dungeons, facing increasingly dangerous challenges. Along the way, he encounters various female characters, each with their own distinct personalities, backgrounds, and abilities. These women gradually form a harem around him, drawn to his strength, leadership, and kindness. The relationships between the protagonist and the women evolve through shared experiences, battles, and mutual reliance, though the dynamics remain rooted in the harem genre's conventions.

The narrative focuses heavily on the protagonist's progression as an adventurer, detailing his strategic use of skills, resource management, and tactical combat. The dungeons are depicted as intricate and perilous, requiring careful planning and teamwork to overcome. The series also explores the societal structure of the world, including the roles of adventurers, merchants, and guilds, as well as the economic and political forces that shape life within and outside the dungeons.

Character development is a key aspect, with the protagonist growing from a novice adventurer into a capable leader. The female characters are given individual arcs that highlight their strengths, vulnerabilities, and contributions to the group. While the harem element is prominent, the story balances it with action, world-building, and the protagonist's personal journey. The series maintains a steady pace, alternating between intense dungeon exploration and moments of camaraderie and emotional connection among the characters.