Minami Iwasaki is a high school student at Ryōō Gakuen High School, where she serves as the class health officer. She has a slender build, mint-green hair, and blue eyes, and is left-handed. Coming from a wealthy family, she resides in Den-en-chōfu, Tokyo. Minami maintains a quiet demeanor and speaks few words, which often leads others to mistake her for being cold, though she is genuinely kind-hearted and deeply cares for her friends. She is sometimes disappointed by her small chest size, a topic occasionally mentioned by her peers.

She lives across the street from Miyuki Takara, and they have been neighbors since childhood. Their similar tastes and shared background allow them to get along well, with Minami sometimes regarded as Miyuki's "little sister" due to her clingy behavior in their younger years. Minami enjoys reading books and playing the piano. Academically, she excels in physical education and demonstrates proficiency in sports, such as accidentally hitting a classmate with a ball during a dodgeball game due to her skill.

She first met Yutaka Kobayakawa during the high school admissions exam, and they were placed in the same class. Minami often assists Yutaka, such as helping her go to the nurse's office when she feels unwell and providing a handkerchief. She exhibits concern for Yutaka's well-being, such as checking if dust in her eyes is tolerable. During a summer festival, she stayed with Yutaka when she felt ill and offered a lap pillow under the starry sky. Minami blushes when Yutaka expresses admiration for her height or talks about her frequently, indicating a close bond. She also feels lonely without Yutaka's presence.

Minami is easily embarrassed in social situations, such as when walking around the school with Yutaka during the cultural festival or when others discuss Yutaka's admiration for her. She has a parasol in her yard and owns a large white dog. Despite her reserved nature, she participates in school activities, including modeling for a café event with themed dresses and waitresses.