Kyōko Kōda

The eldest daughter of the Kōda family. She is four years older than Rei and is his stepsister. She has a fierce temperament and style of shogi play, and was opposed to Rei living with the Kōda family. Her rough temperament was such that some in the shogi community mockingly called her a "poisonous woman." She was a member of the encouragement association, but was forced to quit in her second year of middle school because she could not beat Rei. Deeply hurt by feeling that her beloved father had denied her life, she began to hang out around town. Blessed with good looks and a charismatic presence that attracts people, she has always felt lonely since quitting shogi. She sometimes calls Rei "Zero" and often speaks harshly to him, stirring his emotions, yet she also enters his room to reveal her own feelings, depicting a complex relationship. She harbors feelings for Goto, a married man, and is troubled by their relationship. However, after continuously seeing Goto visiting his terminally ill wife, she comes to understand Rei's feelings of losing his family and being utterly alone, and while regretting her past actions, she wishes for the happiness of both Goto and Rei.

After leaving home, she works as a temporary employee. Momo, having seen her talking with Rei, calls her a "witch" and is scared of her.