Kozue Kusunoki possesses pink hair cut to neck length and blue eyes. She stands 152 centimeters tall with body measurements of 91 (bust, F cup), 54 (waist), and 92 (hips) centimeters. Her typical attire includes a school uniform, often featuring ribbons, bows, and hairclips with butterfly motifs, paired with thigh-high stockings and Gothic Lolita fashion, which she favors.

Generally displaying a reserved and quiet demeanor, she undergoes a notable transformation during quiz-related activities, becoming enthusiastic and energetic, highlighting a contrast to her usual conduct. She belongs to the school's quiz study group club, where her interests include creating aroma candles and participating in quizzes or riddles. A recurring phrase associated with her is "This problem here... I don't understand it."

She is part of a specific circle of friends led by Maaya Mizuno, which also includes Isami, Nanoha, and Youko. Within this group, she maintains social connections but does not hold a leadership position.