Mirin Kazuki appears as a supporting character across Maple Colors media. She possesses orange hair styled in a side-parted bob without bangs, violet tareme-shaped eyes, and a slim, pale teenage body often noted for her large breast size. Her typical attire is a school uniform featuring a miniskirt, vest, and sports visor, frequently complemented by a hairpin.

She attends Kouka Academy as an eleventh grader in class 2-B, designated for problem students. Her placement stems from overtly sexual behavior; she openly engages in sexual activities with minimal prompting, sometimes foregoing condoms with preferred partners, viewing sex as both a passion and pastime. This conduct originates from her upbringing as both parents worked as hosts, influencing her to adopt hostess-like mannerisms. She began practicing seduction on teachers in elementary school, nearly manipulating a principal by junior high, and further refined this skill in high school.

As a member of the school's softball team, she wears her sports visor during activities. She maintains a friendship with young celebrity actress Amu Uzuki and leverages this connection to secure Amu's participation for her class's theater project. Despite her sexual forwardness, her everyday demeanor presents as normal, friendly, and playfully mischievous, often laughing about her seductive exploits.

Within the narrative, she contributes to the central plot of preparing a play to avoid expulsion but shows no significant personal development or change in behavior across official media. Her interactions include teasing the protagonist after he inadvertently witnesses her having sex in a classroom.