The narrative picks up with the protagonist, Charles, a 14-year-old executioner who has beheaded over a thousand people. He reflects on the difficulty of execution, noting that human bones are as hard as iron and that cleanly severing a head requires immense skill, physical strength, and mental fortitude. Charles has just completed an execution, but the applause and cheers of the crowd, celebrating the death of the condemned woman, Henriette Sanson, are unbearable to him. He reveals that Henriette was someone he loved, and he killed her himself, leaving him searching for the reason behind her execution.
Charles resides in Distore, a city where serious criminals are publicly executed as a form of spectacle. He finds this practice morbid and questions the enjoyment people derive from witnessing death. He has been an executioner for six years, and it has been six months since he executed Henriette. His master, Jean Sanson, a portly man and the head of a lineage of executioners, abuses Charles, physically assaulting him and demanding he return to his duties as numerous death row inmates await execution. Jean, unable to bear the emotional toll of execution himself, relies on Charles, his slave, to perform the task. Charles, feigning illness, is threatened with being thrown into a frozen river if he doesn't comply. He despises his life as an executioner but feels trapped, as it's the only way he can remain in his current circumstances.
Deciding to escape, Charles flees into the winter with his executioner's greatsword, intending to sell it for money. He realizes his impulsive departure stems from a desire to die, reflecting on his bleak past: being sold by his gambler parents at seven and bought by the Sanson family at eight. The recent revolution and its aftermath led to a surge of executions, filling his six years as an executioner with the grim task of taking lives.
While walking, Charles is bumped into by a haughty, red-haired girl named Himari Lanfer, who berates him for being in her way. After she leaves, Charles finds a dropped envelope containing an acceptance letter for the prestigious magic academy, "Yunfernodarts," and a test ticket. Despite his initial indifference to magic, Charles recognizes the academy's fame. He decides to return the lost items, seeing it as a final act of good before his intended death.
Following the map on the letter, Charles arrives at the designated test location, which turns out to be a barren area with only a brick wall and a painting of a castle. He hears Himari's voice coming from the painting and, upon touching it, is pulled into the painted world, finding himself before the castle. He encounters Himari arguing with a female examiner. Charles returns Himari's test ticket, receiving no thanks. He learns he can enter because he possesses a unique magic, a secret ritual passed down through the Sanson family, though he is not a formal magician. The examiner, who identifies herself as a teacher from Yunfernodarts, transforms a rat into a sheep with magic. Feeling disoriented, Charles leaves the magical space and collapses outside.
He awakens in a medical room at Yunfernodarts, attended by a short, weary-looking doctor. After recovering, Charles is informed that his natural healing abilities are remarkable. He is then directed to a specific exit, which leads him not outside, but into an arena. There, he is mistaken for a student named Rant Taylor and forced into a practical exam against a three-headed beast, Cerberus. Charles, fueled by his despair and anger over his life, unleashes his Sanson family magic, "Telos Baptisma," a purification ritual that enhances his greatsword. He swiftly defeats Cerberus, astonishing the examiners.
After the exam, the vice-principal, Refil Halman, a peculiar woman who collects broken toys, reveals she has been observing Charles. She recognizes him as the nameless slave executioner from Lanvergue and offers him a scholarship to Yunfernodarts, seeing his combat prowess as a valuable asset. Charles, initially seeking death, is intrigued by the possibility of achieving his dream: to "kill" the death penalty. Halman explains that becoming an "Imperial Magician" is the only way to gain influence to achieve this.
Charles accepts the offer, and Halman provides him with a magically created mansion as his residence for the two months before school starts. He undergoes a series of tests, excelling in physical and mental aptitude but scoring poorly in magic knowledge. He chooses the surname "Sansson" in honor of Henriette.
The narrative then shifts to Charles's past, detailing his first encounter with Henriette when he was a slave and she was a young girl. He adopted the name "Charles" to comfort her after her pet died.
Back in the present, Charles and Halman travel to Yunfernodarts, a school built on an entire island, via a magical submarine train. On the train, Charles encounters Antoine Catarov, a noble from his past who despises him and vows to expel him. He also meets Rant Taylor, a boisterous student who initially mistakes Charles for someone else but eventually recognizes him as the one who defeated Cerberus. Charles, keeping his true abilities and past a secret, befriends Rant. Upon arriving at the island, they witness its impressive scale and diverse areas, including a flying dragon carrying a rider.
