"Shadows House" is a manga series set in a mysterious mansion inhabited by shadowy aristocrats who emit soot, a byproduct of their existence. These shadow nobles are served by living dolls, who act as their faces and voices since the shadows themselves lack distinct facial features. The dolls clean the soot produced by their masters and maintain the household, forming a symbiotic relationship with the shadows.

The narrative centers on Emilico, a cheerful and curious living doll, and her master, Kate, a shadow noble with a calm and thoughtful demeanor. Emilico and Kate share a close bond, which sets them apart from the typical master-servant dynamic seen in the Shadows House. As Emilico begins to uncover the secrets of the mansion, she learns that the relationship between shadows and dolls is far more complex and sinister than it initially appears. The shadows are not merely enigmatic beings but are deeply tied to the dolls in ways that challenge their autonomy and survival.

The story explores the hierarchical structure of the Shadows House, where shadow nobles and their dolls undergo a process called "debut," a formal presentation to the higher-ranking members of the household. Success in the debut is crucial, as failure can lead to dire consequences for both the shadow and their doll. Emilico and Kate navigate this system while uncovering unsettling truths about the origins of the shadows, the purpose of the dolls, and the darker forces at play within the mansion.

Key characters include Shirley and her doll, Rum, who represent a contrasting dynamic to Emilico and Kate, as well as John and Shaun, another shadow-doll pair who become allies in their shared quest for understanding. The narrative delves into themes of identity, autonomy, and the nature of relationships, as the characters grapple with their roles in a system designed to control and manipulate them. The mysteries of the Shadows House unfold gradually, revealing a world where appearances are deceiving, and the line between master and servant is increasingly blurred.