In the world of My Daemon, a Daemon User is a human who has formed a working relationship with a daemon, typically one of the mysterious creatures born from daemonium particles following a nuclear disaster. This relationship is almost universally defined by control and exploitation rather than companionship. Daemon Users employ specialized collars that can deliver an electric shock to their daemon, using this punishment to enforce obedience and suppress the creature's will. The primary motivation for becoming a Daemon User is self-interest. They utilize their daemons' unique powers for a variety of practical and often dangerous tasks, ranging from manual labor and security work to hunting and capturing other daemons for profit. The Peace Organization, a powerful group that researches and seeks to control the daemon population, hires many Daemon Users to act as bounty hunters, sending them to capture valuable or dangerous targets.

In the story, Daemon Users serve as a clear antagonist force to the protagonist, Kento, and his free, uncollared daemon, Anna. They represent the established, fearful order of society that views daemons solely as dangerous tools or threats to be eradicated. While many Daemon Users are ruthless individuals who care nothing for their daemons' suffering, the series introduces some with more complex motivations. For instance, the user Uraga is driven by a desperate need to save his ill brother, showing that some are pushed into this life by circumstance, even if it leads them to commit terrible acts. Other users, like Kaede Houjou with her shield daemon Igisu, prove that not all who use this system are cruel, and that a bond of mutual respect can exist even within its constraints. A key relationship for many Daemon Users is with the Peace Organization, which acts as their primary employer and the authority that legitimizes their actions.

Throughout the series, several Daemon Users undergo noticeable development. Kokonoe, initially presented as a dedicated and threatening agent of the Peace Organization, is ordered to live with and protect Kento. Through this forced proximity, he begins to see the boy as family, creating a conflict between his orders and his growing personal feelings. Similarly, another user named Ando is swayed by witnessing Kento’s unwavering kindness toward Anna, ultimately choosing to let them escape rather than complete her mission. These moments suggest that the rigid, exploitative system of a Daemon User is not absolute and can be challenged by the very empathy it seeks to suppress. The notable abilities of a Daemon User are not about magic or combat prowess, but about the practical application of their daemon's power. A user's effectiveness depends entirely on their ability to command, manage, and strategically deploy their daemon's unique skill, whether it is making objects invisible, storing matter, or creating defensive barriers.