Youko Kishi is a student with violet hair and brown eyes. She stands 160 cm tall, weighs 42 kg, and has body measurements of 80-57-82. Her blood type is B, and her zodiac sign is Libra. Her hobbies include reading literary works and playing the piano.

She had romantic relationships with both Yuuichi and Kotaro. Later, she became pregnant with Kotaro's child but did not initially inform him. The pregnancy was eventually discovered by the school nurse and Yuuichi.