Miyabi Tsukuyomi is a member of the Koi Koi Seven, a group of six girls who protect Gokō Academy and its only male student, Tetsuro Tanaka. She is an adolescent girl with long purple hair that reaches her hips and purple eyes. Her background is largely unexplored in the series; a brief scene shows her cutting her wrist with blood flowing out, suggesting a troubled past that is never elaborated upon. She is quiet, introverted, and highly intelligent, with a strong inclination toward studying and intellectual pursuits. Her analytical mind allows her to assess situations quickly and find solutions, making her the strategist of the group. Despite her reserved nature, she is deeply loyal to her friends and is motivated by a desire to protect the peace of the school, even stating that she will do anything to achieve that goal. She initially struggles to interact with others due to her shyness, but over time she opens up to her fellow Koi Koi Seven members, whom she comes to see as a family. Her most notable ability is the manipulation of her hair, which she can extend, harden, and control at will. She uses her hair as a versatile weapon, cutting through objects, acting as an umbrella, and engaging in combat, particularly against the Zairdrits sent by the student council president, Miya. In the story, she lives in the same dormitory as Tetsuro and the other girls, and she plays a supporting role in battles and daily life. Her character development centers on overcoming her timidity, forming stronger bonds with her teammates, and learning to rely on others as much as they rely on her.