"Aruvu Rezuru - Kikai Jikake no Yōsei-tachi" is a fantasy anime series set in a world where humans coexist with mechanical fairies known as "Rezuru." These fairies are created through advanced technology and serve various roles in society, from assisting in daily tasks to performing complex industrial functions. The story centers on a young engineer named Lute, who specializes in repairing and maintaining Rezuru. Lute's life takes a dramatic turn when a mysterious, malfunctioning Rezuru named Aruvu enters his workshop. Unlike other Rezuru, Aruvu exhibits unusual behavior, displaying emotions and a level of autonomy that defies her mechanical nature.

As Lute investigates Aruvu's origins, he uncovers a hidden conspiracy involving the creation of Rezuru. The series delves into the ethical implications of artificial intelligence and the boundaries between machines and living beings. Aruvu's existence challenges the societal norms that view Rezuru as mere tools, raising questions about their rights and the morality of their creation. Lute becomes entangled in a conflict between those who seek to exploit Rezuru for profit and power and those who advocate for their recognition as sentient beings.

The narrative explores themes of identity, free will, and the relationship between humans and technology. Key characters include Lute, whose technical expertise and compassion drive the story; Aruvu, whose evolving consciousness serves as the catalyst for the plot; and a cast of supporting figures, including rival engineers, corporate executives, and activists, each with their own motivations and perspectives on the Rezuru phenomenon. The series balances its philosophical undertones with action and intrigue, as Lute and Aruvu navigate a world where the line between humanity and machinery becomes increasingly blurred.