Rei’s grande soeur; one of the most well-respected of the Yamayurikai. She is very gifted and good at almost everything, although she is also enigmatic and eccentric. She has a large forehead, which Sei made fun of when they were young, which began their rivalry. She said once that she chose Rei as her sœur to see if anything interesting would happen. She often has friction with Yoshino, as the younger girl is jealous of her bond with Rei. Eriko has four older brothers. After leaving Lillian, she studies Arts. She hates the dentist above all else.