"Is It Wrong to Try to Pick Up Girls in a Dungeon? III" continues the adventures of Bell Cranel, a young adventurer striving to grow stronger while navigating the dangers of the Dungeon. This season focuses on the Xenos arc, introducing a new layer of complexity to the world of Orario. The Xenos are sentient monsters that possess human-like intelligence and emotions, challenging the traditional view of monsters as mindless enemies. Bell encounters a wounded Xenos named Wiene, who displays kindness and vulnerability, forcing him to question the morality of killing monsters.

As Bell forms a bond with Wiene, he becomes entangled in a conflict between the Xenos and the adventurers of Orario. The Xenos seek to escape the Dungeon and find a place where they can live peacefully, but their existence threatens the established order. The Loki Familia, one of the most powerful adventurer groups, views the Xenos as a danger and launches a mission to eliminate them. Bell, torn between his duty as an adventurer and his empathy for the Xenos, resolves to protect Wiene and her kind, even if it means standing against his fellow adventurers.

The season explores themes of coexistence, prejudice, and the blurred lines between good and evil. Characters like Ais Wallenstein, Bell's mentor and unrequited love interest, and Hermes, a god with ambiguous motives, play significant roles in shaping the narrative. The story delves into the struggles of the Xenos as they fight for survival and acceptance, while Bell's unwavering determination to do what he believes is right drives the plot forward. The tension escalates as alliances are tested, and the true nature of the Dungeon's mysteries begins to unravel, setting the stage for future developments in the series.