Matsuzaki-sensei is the physical education teacher and guidance counselor at PK Academy. He is introduced by the protagonist, Kusuo Saiki, as the bad cop in a good-cop-bad-cop dynamic with another teacher, and he is generally feared and disliked by the student body for his strict, no-nonsense approach to school rules. He is first seen conducting a clothing inspection outside the school, confiscating prohibited items and confronting students who try to skirt the regulations. This behavior stems from his belief that school is a place for learning, not leisure, and he is willing to enforce that mindset even if it makes him unpopular.

Despite his intimidating demeanor, Matsuzaki-sensei is not genuinely malicious. Saiki notes that he is actually a good ally for weak-willed students, suggesting that his harsh exterior masks a protective instinct toward those who follow the rules and need support. He respects authority and order, but he is not above getting into physical confrontations when provoked. When the delinquent student Kongou challenges him, Matsuzaki-sensei is about to be beaten before Hatakeyama-sensei intervenes and defeats Kongou. This incident shows that while he is strict, he is not particularly strong in combat and relies on the help of stronger colleagues.

In the story, Matsuzaki-sensei functions as a minor but recurring authority figure whose interactions with the main cast highlight the school's eccentric environment. He has little personal development and no notable superhuman abilities; his role is largely that of a disciplinary figure who occasionally clashed with students but is ultimately respected by Saiki for his straightforward commitment to order. His key relationships are with the other teachers, particularly Hatakeyama-sensei, and with students like Kongou, whom he tries to discipline. There is no indication of deep backstory or significant character growth.