Takahashi Tetsuo, a biology teacher at Shizaki High School, has been fascinated with "demi-humans" since he was in college. He wishes he could have a chance to talk with one, but since the demi-human population is fairly low, he's never even met one.

Machi Kyouko is a dullahan, a demi-human with roots in Irish legend, and one of only three of her kind in the whole world. One day, she stays after school to talk to Tetsuo about her unique problems, and also asks a favor of him.

Kusakabe Yuki overhears some girls saying mean things about her. Gossip is not an uncommon problem among high school girls, but Yuki is particularly worried that it's happening because she's a demi.

Yuki has become a bit more optimistic, thanks to Hikari and Machi. She's learned to trust Tetsuo a bit more since what happened last time, and has decided to tell him what troubles her about her own nature as a snow woman.

Keeping his promise to Himari, Tetsuo visits the Takanashi household to talk to the sisters' parents. Though the twin sisters' names differ by only one letter, Hikari is a vampire, while Himari is an ordinary human.