This story, also called Hebi Onna, is about the legend of the Snake-Woman. It is divided into 3 parts.

1-5. Mama ga Kowai (ママがこわい)
Yumiko's mother is hospitalized. But after being discharged, the mother is acting strange, she quickly reveals to be the Snake-Woman, and she wants to devor the poor Yumiko!

6-14. Madara no Shoujo (まだらの少女)
To recover from the events with the Snake-Woman, Yumiko is sent into the mountains to visit her cousin Kyouko. But at her arrival at the village, the people are afraid of Yumiko, saying that she is the Snake-Woman!

15-29. Hebi Shoujo (へび少女)
(This is the origin story of the Snake-Woman, and also the fourth installment of the Yamabiko Shimai series.)
Youko is a friend of Satsuki and Kanna. Her family is cursed since the time her grand-father injured a snake guardian spirit. After Youko's last relative is killed by a giant snake, a strange woman from a neighbor village adopts her, but somehow, Satsuki is worried about her friend.