Kanata Kanade

Kanata was a girl with incredible talent, who was good at everything she did, leading to her being constantly praised by others and called a genius. Kanata was also rather kind, even towards Haruka, who made no secret of her hatred towards Kanata. Kanata only appears in backstory. Both of Kanata's parents are alive. They appeared to be kind to her, and very proud of her due to her talent. Because of her talent and constant praise, Haruka was incredibly jealous of her. Kanata kept trying to reach out to Haruka, telling her "you can tell your big sister anything", but Haruka kept rejecting her, claiming that Kanata didn't understand her feelings. In fact, Haruka hated Kanata so much, that when approached by Kyubey, made a wish to erase Kanata from existence. The details of Kanata's erasure are unknown, but it can be assumed that Kanata was completely erased from other's memories (except for Haruka's), as she gets no mention before Haruka's backstory is revealed.