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.