Seiichi's younger sister. Although Hotaru was only a high school student, due to Seiichi's influence, she too got inquisitive with the serial disappearance in Lovely Hills town. Like her brother, she believed that Hell Hotline's existence was a urban legend, until one day she paid a visit to Takuma's house regarding Hell Hotline and met Kikuri. Kikuri brought her to a faraway place where Hell Girl resided and showed her the candles, which had names of the people who requested vengeance and the victims who were sent to Hell written on them. Being unable to find Takuma's name on them, she believed even more that Takuma was innocent.