The story begins with Idil Jirahard, a student at the Royal Knight Academy, being summoned by his homeroom teacher. To Idil's indifference, he is informed that he is being expelled due to his poor academic performance, attendance, and attitude. The teacher, a notoriously harsh instructor named Tsargesta, expresses relief at finally being able to expel Idil, who, despite his lack of talent and motivation, came from a prestigious knight lineage, the Jirahard family. Idil's two older brothers are exemplary knights who graduated at the top of their class, and the family's reputation had shielded Idil from expulsion until now. Idil accepts his expulsion, acknowledging his lack of will to improve and his unsuitability for the knightly path.
Upon leaving the academy, Idil returns home to report his expulsion to his father, Harpunk Jirahard, the head of the family. His father, a proud former knight and father of three successful sons, is furious and disowns Idil, calling him a disgrace and demanding he leave and never return. Idil, having anticipated this, accepts his disownment and bids farewell to his mother and younger siblings. His mother weeps, while his younger brother, Agiah, shows contempt, and his younger sister expresses sadness. His two older brothers, Zectworris and Exarga, are away on knightly duties.
Freed from the expectations of his family and the academy, Idil finds solace and purpose at the Adventurer's Guild, where he has been secretly active as an adventurer. He earns his living through quests, which explains his poor attendance at the academy. He reveals to a guild staff member, an old friend named Old Man, that he has been expelled and disowned. Old Man, amused by Idil's "typical noble downfall" trope, informs him that a B-rank party has invited him to join, but Idil politely declines, stating he wants to focus on his personal research.
Idil's research involves a rare magic he learned from a mysterious bard: "Bond Summoning." This magic allows him to summon objects from other worlds by forming a bond with monsters. He explains that his aptitude tests for various adventurer classes were all mediocre, and he never achieved true mastery, much like his struggles as a knight candidate. The bard taught him that while he can learn many things, he cannot reach the pinnacle of any skill, but he is uniquely suited to this lost ancient art.
Idil's first experiment with Bond Summoning involves a slime he defeated in the dangerous Ideonir Greatwood, a vast and perilous forest. He successfully forms a bond with the slime, which he names "Cuppi," and can now summon water from it without a container. This proves incredibly useful for survival. He then encounters goblins and, with Cuppi's help, summons "lotion" to incapacitate them, allowing him to defeat them with a spear. He also learns that he can only have one bonded monster at a time until his Bond Summoning level increases.
His next target is a powerful golem. Instead of defeating it, Idil attempts to form a bond. To his surprise, he succeeds, and the golem transforms into a young girl named VOL-4071CX2, an "all-situation automaton" with a powerful combat module called "Gigant." She pledges her loyalty to Idil as her master. Idil discovers that his Bond Summoning level has significantly increased, and he can now summon different types of "enhanced external modules" from the automaton.
Meanwhile, at the Royal Knight Academy, the teacher Tsargesta is proud of his "perfect class," the "Golden 139th term," which includes talented students like Prince Mashhada. He is pleased with Idil's expulsion, seeing him as a stain on the class. However, Prince Mashhada confronts Tsargesta, revealing that he had been observing Idil and recognized his hidden potential, having been second in class until his fourth year. Mashhada reveals that Idil was secretly an accomplished adventurer, even defeating a wyvern, and that he had planned to take Idil under his direct tutelage after graduation. Tsargesta's actions have ruined this plan, leading Mashhada to have him demoted to a foot soldier on the frontier.
Back in the Ideonir Greatwood, Idil's family is in turmoil. His father, Harpunk, celebrates his successful sons and the expulsion of Idil. However, his second son, Exarga, is disgusted by his father's cruelty and the family's obsession with status. He confronts his father and, with the tacit approval of his eldest brother, Zectworris, who is indifferent to family matters, disowns his father and leaves the family, intending to find and protect Idil.
