Yozora Mikazuki

Sora, 三日月夜空

Yozora is described as being cruel and selfish, with black hair. She claims to understand and respect bullying but resents when others call her a bully herself. Her difficult personality drives people away before she meets Kodaka. She is physically abusive towards Sena and argues with Maria, manipulating her into giving up an empty room for the Neighbors Club. Yozora also tricks Yukimura into working as a crossdressing cosplay maid for the club. The only person she cannot insult is Rika, who turns her insults back on her with dirty jokes that leave her exhausted. As a result, Yozora does whatever Rika says, such as crossdressing.

Spoilers:

She is Kodakas childhood friend, though at the time, he believed that she was a boy, calling her "Sora"; her nickname for him was "Taka." On the day that Kodaka moved, she intended to wear a skirt and reveal her gender to him but was too embarrassed to do so. She seems to have feelings for Kodaka. It is revealed in the Volume 9 of the light novel that Yozoras original surname was Hidaka. Her father abandoned her and her mother due to the interference of another woman. Yozora tried to cheer her mother up, only to unintentionally madden her in the subsequent process, resulting her mother hurting her with a kitchen knife. Because of such an incident, it left a giant scar in her mind and she lost trust in people around her, resulting in the cruel facade she puts up later on in her life. It is implied through out the novel but is finally revealed in volume 7 that the only reason Yozora made the club was to spend time alone with Kodaka; and that she had no interest in gaining friends in the first place