"Devils and Realist" is a supernatural manga series that blends elements of fantasy, comedy, and drama. The story centers on William Twining, a brilliant and pragmatic young aristocrat in 19th-century England. As the sole heir to the prestigious Twining family, William is a staunch realist who values logic and reason above all else. His life takes a dramatic turn when he discovers that his family has fallen into financial ruin. Determined to restore his family’s status, William sets out to secure a scholarship to continue his education at the prestigious Eden College.

William’s plans are disrupted when he inadvertently summons a demon named Dantalion, one of the 72 Great Dukes of Hell. Dantalion reveals that William is the "Elector," a human chosen to determine the next ruler of Hell, as the throne has been left vacant after Lucifer’s fall. This revelation thrusts William into a world of supernatural intrigue, where demons, angels, and other celestial beings vie for his favor. Despite his skepticism, William is forced to navigate this chaotic realm while maintaining his commitment to rationality.

The series explores the tension between William’s unwavering belief in logic and the fantastical reality he is thrust into. Key characters include Dantalion, who serves as William’s primary guide and protector; Sytry, another demon who seeks to manipulate William for his own purposes; and Isaac Morton, William’s loyal friend and classmate, who becomes entangled in the supernatural events. The narrative also introduces figures from biblical and demonic lore, such as the archangel Uriel, who plays a pivotal role in the celestial power struggle.

As the story progresses, William’s role as the Elector becomes increasingly significant, with various factions attempting to influence his decision. The manga balances its supernatural elements with moments of humor and character-driven drama, particularly through William’s interactions with the eccentric and often absurd beings he encounters. The series delves into themes of power, morality, and the clash between belief and skepticism, all while maintaining a focus on William’s journey as he grapples with his newfound responsibilities and the challenges they bring.