She is Keita's younger sister who has those Chinese bun hair style.
Mika Tsuwabuki is created by Yoshiaki Sukeno as the supporting characters in the Binbogami Ga! manga series. She has no information regarding any inspiration used by Yoshiaki Sukeno for her creation. She makes her first manga debut in volume 1: chapter 2 and first anime debut in episode 3. She is voiced by Ayami Yoshii.