Beryl Gardinant, a self-proclaimed humble old man, has spent the past twenty years as the sword instructor of a small, rural dojo in a remote village. His life is quiet and unassuming, a stark contrast to his younger days when he dreamed of glory as a master swordsman. This peace is shattered when a former student, Allucia Citrus, now the Commander of the Royal Order of Knights, arrives with world-shattering news: by imperial command, Beryl has been appointed as the special instructor for the knights of the Liberion Order. Unable to refuse, the middle-aged swordsman travels to the bustling capital, a world far removed from his backwater home.

Upon his arrival, Beryl is quickly overwhelmed, not only by the city's scale but also by the remarkable success of his past pupils. He reunites with a series of formidable former students, including the elite knights under Allucia's command, the ace wizard Ficelle Harbeller who serves in the Magic Corps, and Surena Lysandra, an adventurer who has attained the guild's highest black rank. Despite his self-deprecating nature and insistence that his students' accomplishments are their own, Beryl's own abilities prove to be extraordinary. His seemingly simple swordsmanship, honed by decades of discipline and instinct, easily overcomes challenges, including a duel with the skeptical Vice-Commander Henbritz, quickly earning him a reputation as the backwater swordmaster.

The first major narrative arc establishes Beryl in his new role, navigating the politics of the royal court and the dangerous monster-hunting quests of the Adventurer's Guild. A significant turning point occurs when Beryl encounters a young pickpocket named Mewi Freya. Seeing the despair in her eyes, he rescues her from the clutches of a shadowy criminal organization and becomes her reluctant guardian. This leads to a heartfelt arc focused on parenting, as the aging bachelor learns to care for the girl, managing her enrollment in a magical institute and adjusting to life as a father figure.

The season builds toward a political conspiracy involving a neighboring country's delegation. Beryl is assigned to guard the royal family during their tour of the capital. However, a flood of fanatical assassins threatens the event. The mastermind is revealed to be Rose Marblehart, the Vice-Commander of the Holy Order of the Church of Sphene and yet another of Beryl's former students. Unlike the others who idolize him, Rose holds a different, more sinister ideology. The final arc culminates in a personal and emotional duel between master and student, as Beryl is forced to draw his sword against Rose to uncover her true intentions and put a stop to the conspiracy. A second season has been announced and is scheduled to air in July 2026.