Beryl Gardenant is a middle-aged man who serves as the central protagonist of this story. He is the master of a swordsmanship dojo located in a small, remote mountain village in the kingdom of Reberis, a position he has held for many years. Despite his humble origins, his reputation as a legendary teacher, known as the Backwater Swordsman or the Sword Saint of the Countryside, has spread throughout the kingdom because several of his former students have gone on to become famous heroes and adventurers.

In terms of personality, Beryl is defined by his profound humility and self-deprecating nature. He consistently downplays his own immense abilities, thinking of himself as nothing more than a simple old man from the countryside who happens to run a dojo. He is a genuinely kind and good-hearted gentleman who is easygoing and laid back. This unassuming demeanor often leads others to underestimate him until they witness his skill in combat. Beryl is also notably oblivious to romantic interest. Several women, including his former pupils like Allucia and Surena, have shown clear affection for him, but he either fails to notice these advances or dismisses them due to his inexperience and the perceived inappropriateness of the relationships, often citing his role as their teacher and his older age. His one clear passion outside of swordsmanship is a deep fondness for drinking ale.

Beryl's primary motivation is to pass on his knowledge of the sword to the next generation. His humble goal is simply to teach, and he finds his greatest fulfillment in the success and growth of his students. He is forced to leave his village and take on a new role as an instructor for the royal knights in the capital city of Baltreine, largely due to the machinations of his former student, Allucia Citrus, and the wishes of his father. In his role in the story, Beryl acts as a mentor archetype and an experienced protagonist. He is thrust into a wider world where his skills are truly tested against supernatural threats, powerful knights, and other formidable fighters, all while he continues to teach and protect those under his care.

Beryl has several key relationships that define him. His relationship with his father, Moldea Gardenant, is one of respect mixed with exasperation, as his father constantly pressures him to marry and produce an heir. Among his students, Allucia Citrus, the knight captain who invited him to the capital, is one of the most prominent. He cherishes her but is uncomfortable with her romantic feelings for him due to their age difference and teacher-student dynamic. Surena Lysandra is another significant student whom he took in as a traumatized child and nursed back to health, creating a lasting paternal bond. He also becomes an adoptive father to a young girl named Mewi Freya, whom he saves from a dire situation and cares for deeply, though he often worries about being overbearing. His friendship with Lucy Diamond, the head of a magic institute, provides him with a valuable ally he trusts implicitly.

Throughout the story, Beryl undergoes significant development as he gradually comes to grasp his true level of skill. Initially, he genuinely believes he is just an average swordsman, assuming his victories over powerful opponents are due to them holding back. As he faces more challenging foes and receives perspective from his worldly students, he slowly realizes that his abilities are, in fact, among the best on the continent. A pivotal moment in this realization is finally defeating his own father in a sparring match. He also develops from a reluctant participant forced into a new life to a more confident, though still humble, protector and instructor in the capital, while also navigating the challenges of being a new father.

Beryl's notable abilities are rooted in practicality and technique rather than flashy moves. He is a master swordsman whose real strength lies in his analytical mind, allowing him to observe an opponent's technique and construct a perfect counter within an incredibly short span of time. His style is boring, but practical, relying on perfect stance, expert awareness of distance, and flawless execution. He is a master of the counter-attack, using it to instruct his students and defeat faster, stronger enemies. His super-reflexes and exceptional kinetic vision are often highlighted as his most outstanding physical traits. He is also a combat pragmatist who does not hesitate to use unconventional or dirty maneuvers to win, such as grabbing an opponent's clothing to throw them off balance. He wields a unique longsword forged from the bones of a griffin he slew, a blade of incredible sharpness and durability. Despite his age, he possesses great agility and endurance.