Henzan Sensei is a character introduced in the second season of the anime, serving as the new homeroom teacher for Reina Aharen, Raido Matsuboshi, and their classmates as they begin their third year of high school. She is a rookie educator, entering the profession with a spirit that is both earnest and enthusiastic, though she noticeably lacks practical experience. Her youthful and child-like appearance contrasts with her lively personality and her strong, almost unwavering determination to be a passionate teacher, a dream she has held since watching a drama about teaching as a child.

The core of Henzan Sensei’s personality is her rigid, by-the-book approach to her duties. She frequently carries and consults the school handbook, trying to find proper procedures for every situation she encounters as an educator. This methodical nature leads to her primary source of conflict and humor: a profound and comical misinterpretation of the school's social landscape. Prior to her arrival, she was warned by another teacher, Tobaru Sensei, about the "esteemed" couple, Aharen and Raido. However, she completely misconstrues this warning, believing that "esteem" refers to physical danger and that her new students are violent delinquents. Consequently, she is terrified of Aharen and Raido, whose bizarre but benign antics—such as extreme stretching—only serve to reinforce her mistaken belief that they are dangerously unpredictable.

Her primary motivation is to successfully fulfill her role as a homeroom teacher, maintain order according to the school’s rules, and earn the respect of her students, even as she remains perpetually overwhelmed by them. In the story, she acts as a new authority figure who inadvertently highlights the quirky and wholesome nature of the main cast through her exaggerated, fearful reactions. Her relationships with other faculty members are key to her initial development. Tobaru Sensei and the school nurse, Miyahara Sensei, act as senior colleagues and mentors, with Tobaru giving her practical advice on not overthinking her job and learning to rely on both her colleagues and her students. Through these interactions, Henzan Sensei shows signs of growth, moving from a state of sheer panic to a slightly more grounded, though still easily flustered, teacher trying to find her footing.

One of her notable abilities is a physical gag shared with Tobaru Sensei: she experiences nosebleeds when her senses are overwhelmed by the "ahare"—the indecipherable or overwhelming charm and actions—of the students. Her unwavering, single-minded determination to charge forward and do her job correctly is also a defining trait, even when she is visibly struggling and running away in shame from her perceived failures.