Mariko Izumo is a teacher at Tsujido High School and a notable figure in the early part of the story. She first appears during a summer holiday on Yoron Island, where she and her friend and colleague Ayumi Murakoshi pretend to be college students and meet Eikichi Onizuka and Ryuji Danma, who are also lying about their identities. After a series of comedic misunderstandings, she discovers that Onizuka and Danma are actually high school students. Once she returns to school, she initially seeks revenge for the earlier embarrassment, but over time she reconciles with the pair. She is the daughter of a yakuza boss and was formerly a member of an all-girl gang known as the Red Rouge Ladies or Purple Haze. Her past includes a rebellious youth, having lost her virginity at age thirteen to her home tutor, and she has a determined, assertive personality. She is direct about pursuing what she wants and can be both playful and manipulative when needed. Despite her wild streak, she cares deeply about her students and often acts as a protective and supportive figure. After Ayumi Murakoshi leaves the story, Mariko becomes a recurring ally who frequently helps Onizuka and Danma out of difficult situations, offering information, advice, and occasional physical assistance. Her relationship with Onizuka evolves from antagonism to genuine mutual respect, and she serves as an emotional anchor for the duo during several critical moments. She also maintains a close friendship with Ayumi and provides guidance during Ayumi’s romantic struggles. Mariko is resourceful and has a range of practical skills, including knowledge of the red light district, expert makeup application, and an unusually limber body. She is not afraid to use her family's yakuza connections to intimidate or resolve problems, but she also shows a softer, more maternal side when comforting those in distress. Her development is marked by a transition from a self-centered, hedonistic young woman into a more responsible and caring figure, though she retains her bold and confident nature throughout.