"Makai Ouji - Devils and Realist" is a supernatural fantasy anime based on the manga by Madoka Takadono and Utako Yukihiro. The narrative centers on William Twining, a brilliant and aristocratic young man who prides himself on his rationality and skepticism. As the heir to the prestigious Twining family, William is a realist who dismisses the existence of the supernatural, relying solely on logic and reason. His life takes an unexpected turn when he discovers that he is the "Elector," a human with the power to choose the interim ruler of Hell during a crisis in the demon world.

The story begins with William facing financial ruin due to his uncle's mismanagement of the family estate. While searching for valuables to sell, he inadvertently summons a demon named Dantalion, one of the 72 Pillars of Solomon. Dantalion reveals that Hell is in chaos following the disappearance of its ruler, Lucifer, and that William's role as the Elector makes him crucial to resolving the power struggle among demons. Despite his disbelief, William is thrust into a world of angels, demons, and supernatural politics, where his decisions carry immense consequences.

Throughout the series, William interacts with various demons and celestial beings, each vying for his favor to secure the throne of Hell. Key characters include Dantalion, a loyal and protective demon who serves as William's guide; Solomon, a legendary king with a mysterious connection to the demon world; and Sytry, a cunning and manipulative demon with his own agenda. William's pragmatic nature often clashes with the fantastical elements of his new reality, but his sharp intellect and resourcefulness allow him to navigate the complexities of the demon world.

The plot explores themes of power, morality, and the clash between rationality and the supernatural. As William delves deeper into the demonic hierarchy, he uncovers secrets about his own lineage and the true nature of his role as the Elector. The series balances intrigue and humor, with William's dry wit and skepticism providing a counterpoint to the over-the-top personalities of the demons and angels he encounters. The narrative builds toward a climactic resolution as William must decide whether to embrace his role in the supernatural world or reject it entirely, all while grappling with the implications of his choices on both the human and demon realms.