My Funeral - The Cursed Snake Classroom/The Curse of the Black Hair

(from ebookjapan):
If you kill the snake, you will have a terrible haunting.... As her classmates throw stones at the snake, Mika recounts a horrifying incident from six months ago. It happened during gym class. Mika, who hates snakes, is startled by a white snake that suddenly leaps into her field of vision, and she forgets herself and kills it....

Note: Volume 1 contains The Cursed Snake Classroom and another work, Volume 2 contains *Curse of the Black Hair* and other works. The two volumes are digital editions of Koga's Tairiku Shobo tankobon. Curse of the Black Hair was serialized in Funny, the sister magazine of COM.