She used to live in a rural village called Tsukinose. Others at school call her Nikaido. She is level-headed and respected by everyone. She lives alone in an ordinary house, away from her mother. In the past, she had a tomboyish personality and short hair. After moving, she changed her appearance and personality; she is now diligent, always uses polite speech, and excels at her studies. However, when she is with Hayato, her first person pronoun becomes 'Boku' (soft/boyish) and she acts like a young boy. She occasionally visits Hayato's house to play games with him or talk to Himeko. She is close with Himeko. Surprisingly, her physical distance with Hayato remains as close as it was in the past, like male friends. She has long hair and is shorter than Himeko. She occasionally teases Hayato or does things to make him feel embarrassed.

She lived in the rural village of Tsukinose. She is Hayato's younger sister and a third-year middle school student. She is self-conscious about being from the countryside and puts more effort into fashion than most. She is on good terms with Haruki and calls her Haru-chan. Unlike Hayato, she owns a smartphone and contacts Haruki almost every day. She gets along quite well with Hayato too. She used to play with Haruki in the past.