Dragon Head, Volume 1 (Dragon Head, #1)

The end of everyone was just the beginning...
Returning home by train after a class trip, Teru Aoki takes a most frightening ride inside a mountain tunnel. When the train derails, nearly everyone aboard is killed. Amidst the bloody carnage, Teru discovers two survivors - but salvation is far from their grasp. As they try to dig out from the wreck in order to come up with a plan to stay alive, the lack of light and food, combined with the stench of death and decay, will lead one member of the group down a dark and demented path. And with sudden, violent earthquakes shaking the tunnel, escaping to the outside world may lead them to an even greater danger...