by SUENOBU Keiko
Konno has lived her life with indifference to and acceptance of the way things work in both society and school. But when her school bus has an accident, leaving her one of five survivors trapped by a cliff, the situation forces her to learn many lessons about herself and others as she tries to survive until rescue comes.
Scanlated: Doko Demo Doa
Downloads: extremely difficult, but a few are available on manga online reader sites
I bought the first 4 volumes so I could get the rest of the story as access to the scanlations are weird...
Volumes for sale