Erika Sendou
Erika is also a fifth-year student, as well as the student council vice-president. She is strong in literature classes and martial arts, and is very attractive, making her popular in her school. She has an inquisitive personality, and likes to do things directly. Once she has her mind set on something, she becomes very pushy, and will take her time making plans to make sure she gets her way. Her older brother Iori is the student council president.
In the manga, it is revealed from Seiichirou that he and Erika are blood brother and sister. She was given away to Sendou family as requested by Kaya Sendou.
Later in the manga, she and Kouhei start dating. She takes up the offer from her mother to live as a normal human and gets her blue crystal from her body to be destroyed.