Azusa Fuyutsuki is a 22-year-old teacher at Holy Forest Academy, where she serves as the Japanese language instructor. Born in Tokyo on March 19th, she represents a sharp contrast to her more famous colleague, Eikichi Onizuka, having graduated from the prestigious Waseda University with a degree in Literature. Her decision to become an educator was inspired by her own high school teacher, Saito.

Physically, Azusa is a pale-skinned young woman with neck-length brown hair and brown eyes. She is notably self-conscious about her figure, particularly the size of her chest, a source of insecurity that is played for humor at various points in the story. She lives alone in an apartment.

Initially, Azusa presents as shy, quiet, and quite ordinary. However, as the narrative progresses, she reveals a core of determination and boldness, especially when defending something she believes is important. She holds her role as an educator in high regard, placing a strong emphasis on the responsibility to teach and nurture students, rather than simply collecting a paycheck. Despite her strong moral compass and responsible nature, she can become upset, argumentative, and offended. Her lack of confidence in her own teaching abilities is a significant internal struggle, one that Onizuka helps her overcome by assuring her that she has taught him something valuable. She envies the sheer joy and conviction Onizuka brings to his work, admiring his willingness to stand by his beliefs even when facing overwhelming opposition. By the end of the series, she has matured into a more confident senior teacher who can offer advice to new faculty members, crediting Onizuka as the one who taught her what it truly means to be a teacher.

Azusa's role in the story is primarily that of Onizuka's supportive coworker and, eventually, a romantic interest. As she worries about him throughout his many reckless escapades and dangerous situations, her feelings for him grow, though she is reluctant to admit them openly, often insisting they are merely friends. Her quiet, by-the-book nature serves as a perfect foil to Onizuka's loud and unconventional methods, highlighting the central themes of the narrative. She frequently puts her own job on the line to assist him, demonstrating the profound influence he has on her.

Her relationships with others at the academy are complex. She is extremely popular with the male students, which creates intense jealousy and animosity from the female students in her class. This leads to her being ostracized and targeted with pranks, such as having water thrown on her in the bathroom, causing her to question her effectiveness as a teacher. Onizuka's advice helps her navigate this difficult dynamic and eventually win over the girls. She is also the object of obsessive affection from fellow teacher Suguru Teshigawara, a brilliant but deeply disturbed stalker who views her as his ideal woman and despises Onizuka for capturing her attention.

Azusa's personal life includes her younger sister, Makoto Fuyutsuki, who is a high school student and radically different from her. Unlike the reserved Azusa, Makoto is an expert in martial arts, obsessed with detective investigations, and skilled with technological devices. Among Azusa's notable abilities are her proficiency with technology and her passion for detective work. She is also capable of bizarre and extreme measures when motivated, such as creating a mountain of jelly studded with tuna eyes or preparing a whole grilled tuna head in a misguided attempt to help Onizuka study, demonstrating a hidden eccentric streak that runs in her family.