Kurumi Momoka (来海ももか) was Erika's older sister. She was a 17 year old second year high school student at Myoudou Gakuen High School, but she also worked as a fashion model.

Momoka was a very famous and popular model, even appearing on various magazine covers. But sometimes her work (photo shoots on the weekdays) made her miss school, so she didn't have many friends in her class. Many of the other students aslo looked at her as a "star" and not as a classmate. Her only friend was Tsukikage Yuri. Momoka had her heart flower taken in episode 8.