Rei Hikawa is a Japanese woman characterized by blonde hair and green eyes, possessing physical measurements of 90-57-86. She leads a double existence: outwardly immersed in the world of tennis while privately entangled in an inappropriate relationship with her younger sister. This secret familial dynamic is exposed when Mr. Shibui uncovers her actions. He intervenes, confronting Rei and imposing punishment for her behavior. The character features across multiple episodes of her series.