"Queen's Quality" is a supernatural shōjo manga series that blends action, romance, and psychological elements. The story centers on Fumi Nishioka, a young girl with a mysterious past who possesses the ability to control "bugs"—malevolent entities that infect and manipulate human minds. Fumi is taken in by the Kuhoin family, a lineage of "Sweepers" tasked with eliminating these bugs and protecting humanity from their influence. Kyutaro Horikita, a skilled Sweeper and member of the Kuhoin family, becomes Fumi's mentor and protector, guiding her as she learns to harness her powers.

As Fumi trains to become a Sweeper, it becomes evident that her abilities are far more potent and complex than initially understood. She is revealed to be a potential "Queen," a rare and powerful figure capable of either cleansing the world of bugs or plunging it into chaos. This duality creates tension, as Fumi struggles to control her darker impulses and the growing influence of the "Black Queen," a malevolent force within her that seeks to corrupt and dominate. The narrative explores her internal conflict, as well as her relationships with Kyutaro and other members of the Kuhoin family, who are determined to help her resist the Black Queen's influence.

The plot delves into the history of the Kuhoin family and their ongoing battle against the bugs, revealing deeper conspiracies and hidden truths about the origins of these entities. Fumi's journey is intertwined with the broader struggle between Sweepers and their adversaries, including rogue Sweepers and powerful bug-infested individuals. The series balances intense action sequences with moments of emotional depth, particularly in Fumi's evolving bond with Kyutaro, which transitions from mentorship to a deeper, more personal connection.

Themes of identity, self-control, and the struggle between light and darkness are central to the narrative. Fumi's growth as a character is marked by her determination to protect those she cares about while grappling with the fear of losing herself to the Black Queen. The manga maintains a steady pace, alternating between high-stakes battles and quieter, character-driven moments, creating a compelling and multifaceted story.