A hundred years before the story begins, the world was unified for the first time into a single kingdom called Astoria. Now, as the fifth king prepares to step down, a brutal selection contest known as the Tessère is held to choose the next sole ruler of the realm.

The protagonist is Tarte Aupoir Croqmonsieur, a young noble born into immense wealth, power, and magical talent. Convinced that the crown is his birthright, he is arrogant and dismissive of commoners. On the day of graduation, he is publicly challenged to a duel by Figo, a blacksmith's son he had previously bullied. To Tarte’s utter humiliation, Figo wins, revealing that Tarte’s strength was merely an illusion propped up by his father’s money and influence.

Shattered by this defeat, Tarte is forced to confront the fact that he possesses nothing of his own. To prove his worth, he decides to abandon his privileged life and run away from home to start from zero. His father, however, assigns a talented maid and Tarte’s cynical former teacher, Romeo, to accompany him as reluctant mentors. Romeo, known as a "dejected loser" who failed his own King Selection exam in the past, now guides Tarte through harsh lessons about the real world.

As Tarte travels to prepare for the Tessère, he encounters other contenders for the throne, most notably Kazilla, a half-human, half-monster outcast who dreams of becoming king to reconcile humans and monsters. Initially rivals, Tarte and Kazilla eventually become traveling companions. The series follows Tarte’s journey from a spoiled, detestable prince into a resilient underdog striving to earn his place through grit and self-discovery. Written and illustrated by Shinachiku (also known as Chihiro Watanabe), a former assistant to Kohei Horikoshi of My Hero Academia, the manga began serialization in Japan in 2024.