Akuto Sai, a high school student with aspirations of becoming a high priest to bring peace to the world, enrolls in Constant Magical Academy. However, upon arrival, a system known as the "Demon King Program" predicts his future as the next Demon King, a figure destined to bring chaos and destruction. This revelation shocks the academy and its students, creating immediate tension and mistrust around Akuto. Despite his genuine intentions, the prophecy begins to shape his interactions and the unfolding events.

Akuto is joined by a diverse group of characters, each with their own motivations and connections to the prophecy. Korone, an android observer sent by the government, monitors Akuto’s actions to ensure he does not fulfill the Demon King role. Junko Hattori, a skilled swordswoman and classmate, initially opposes Akuto due to her family’s duty to oppose the Demon King but later becomes an ally. Keena Soga, a carefree and mysterious girl, forms a close bond with Akuto, though her true nature and origins remain enigmatic. Hiroshi Miwa, Akuto’s childhood friend, provides comic relief but also plays a role in the larger narrative.

As the story progresses, Akuto grapples with the growing influence of his Demon King powers, which manifest despite his efforts to resist them. The academy becomes a battleground for various factions, including religious organizations, government agencies, and magical entities, all seeking to control or eliminate Akuto. The narrative explores themes of destiny, free will, and the nature of power, as Akuto struggles to reconcile his desire for peace with the destructive path laid out for him.

The plot delves into the origins of the Demon King prophecy, revealing ties to ancient conflicts, advanced technology, and the manipulation of societal systems. Akuto’s journey is marked by battles, political intrigue, and personal growth as he confronts adversaries and allies alike. The series balances action, humor, and philosophical questions, creating a layered narrative that examines the complexities of morality and identity.

By the conclusion, Akuto’s choices and the actions of those around him reshape the world’s understanding of the Demon King and the systems that govern it. The story leaves room for interpretation regarding the true nature of destiny and the potential for change, even in the face of seemingly insurmountable odds.