"Shadows House" is a gothic mystery anime set in a sprawling mansion inhabited by shadowy aristocratic figures known as the Shadows. These enigmatic beings are accompanied by living dolls, who serve as their faces and voices, as the Shadows themselves are made of soot and lack distinct features. The dolls, referred to as "living dolls," are tasked with maintaining the Shadows' appearances and managing their daily lives. The story primarily revolves around Emilico, a cheerful and curious living doll, and her master, Kate, a Shadow who is kind and introspective. Their relationship forms the emotional core of the narrative.

The Shadows House operates under a strict hierarchy, with the aristocratic Shadows residing in the upper floors and their living dolls in the lower quarters. The Shadows are shrouded in mystery, and their origins and purpose are gradually revealed as the story progresses. Emilico and Kate navigate this complex world together, uncovering secrets about the mansion, its inhabitants, and the true nature of the Shadows. The narrative explores themes of identity, autonomy, and the blurred lines between master and servant, as Emilico and Kate challenge the established order of the Shadows House.

As the series unfolds, Emilico and Kate encounter other Shadow-doll pairs, each with their own dynamics and struggles. Notable characters include Shaun and John, a diligent living doll and his energetic Shadow master, and Lou and Louise, a reserved pair with a more formal relationship. The interactions between these pairs highlight the varying degrees of trust and control within the Shadows House. The story also introduces antagonists, such as the strict and manipulative Star Bearers, who enforce the mansion's rules and maintain its secrets.

The plot thickens as Emilico and Kate uncover unsettling truths about the Shadows House, including the fate of living dolls who fail to meet expectations and the mysterious "debut" ceremony, where Shadow-doll pairs are evaluated for their compatibility. The series balances moments of lighthearted camaraderie with darker, suspenseful elements, creating a compelling narrative that keeps viewers engaged. Through its intricate world-building and character-driven storytelling, "Shadows House" presents a thought-provoking exploration of power, loyalty, and the search for self-identity within a gothic, enigmatic setting.