Kouko is a girl of very small build and height, and has slightly tanned skin. She has short, somewhat spiky light brown hair and wide brown eyes. She wears the winter Santa Orchidea Senior High uniform but keeps both her shirt and her sweater's sleeves rolled up at all time. She prefers the short skirt model due to its practicality.
Kouko shows herself as a brash, overly energetic individual to others; having no discrimination as to who to talk to. As the PE teacher's assistant and as the track team leader, she shows some talent for leadership; keeping a strong pulse and making herself heard despite her small build. She feels the need to help others; even if the people in question don't wish for her help in the first place. Therefore, she sneaks around searching for problems and does not hesitate to butt in a personal matter to try to help. This makes her, while very loved by the boys and the students in general, quite a threat to anyone's privacy.
Though her name is "Kouko", the kanji used is more commonly read as "Akiko". Despite that, girls with the same kanji reading as Kouko are not particularly rare.