Kyougo Sekime is the school doctor at Osaka High School, a boarding school primarily for male students. He is an adult staff member living on campus, which places him in a unique position as an authority figure who is also deeply integrated into the daily lives of the student body. His physical appearance is notably youthful, often causing new students to mistake him for a peer rather than a doctor or faculty member.

In terms of personality, Sekime is generally laid-back, observant, and somewhat mischievous. He possesses a dry sense of humor and often appears amused by the chaotic energy of the students around him. Despite his casual demeanor, he is highly perceptive and rarely surprised by the antics of the main characters. He tends to speak in a calm, measured tone and rarely raises his voice, preferring to solve problems through observation and subtle intervention rather than overt discipline.

Sekime’s primary motivation revolves around maintaining the health and well-being of the students, though he seems particularly interested in the more eccentric individuals. He is driven by a professional curiosity and a genuine, if understated, sense of duty. Unlike the teaching staff who focus on academics and rules, his concern is strictly physiological and psychological, allowing him to act as a non-judgmental confidant.

His role in the story is that of a guardian and a secret-keeper. He is one of the very few characters who quickly deduces the protagonist’s secret. Rather than exposing the truth, he chooses to observe and protect the situation, offering medical assistance and a safe space when necessary. He acts as a stabilizing force, providing a quiet sanctuary away from the competitive sports and romantic entanglements. His office often serves as a neutral ground where characters can rest or discuss sensitive issues.

Regarding key relationships, Sekime maintains a professional yet familiar connection with the protagonist. He is protective of her secret but enjoys the intrigue she brings. He also interacts frequently with the other students, particularly those who frequently get injured, such as the track and field athletes. While he is an adult, he does not typically assert rigid authority over the teachers or headmaster, preferring to operate in the background. His relationship with the school's chairman is one of professional respect, as he is given a long leash to run the infirmary as he sees fit.

The character shows little to no dramatic development over the course of the series, as he is a static supporting figure. His consistency provides stability; he remains the same perceptive and relaxed doctor from his first appearance to the last. The evolution is more in how other characters come to rely on him, but his own worldview and actions remain steady.

Notable abilities include his medical expertise, which is implied to be considerable enough to handle sports injuries and general illnesses without needing to send students to an external hospital. More importantly, he has a remarkable ability to keep secrets and maintain a poker face. His observational skills allow him to see through disguises and lies almost instantly, yet he is equally skilled at pretending not to notice. This ability to balance awareness with discretion is his most defining trait.