Kiyo is a girl who first appeared at Misao's school, asking her to stay away from Kyo because she wanted him instead.
She is, in fact a snake demon who tried to poison Misao. She warns Kyo that if he sucks the poison out he could die, but Kyo does it anyway, much to her surprise. She escapes while Kyo is helping Misao. She (along with her brother, Kensuke) later helps Kuzunoha try to take Misao away from Kyo, but she finds out Kuzonoha tricked her, as he planned to kill Kyo (something she didn't want to happen as she still deisred him). During the ensuing commotion where Kyo finally killed Kuzonoha, she escapes again.