Dragon Head (2003)

Based on the manga of the same name by Mochizuki Minetaro. On the way home from a school trip, a tragic accident traps Aoki Teru's express train in a collapsed tunnel. The only other survivors of the catastrophe are his classmates, Seto Ako and Takahashi Nobuo. Teru resolves to escape to the surface, braving death, danger, and madness. But what awaits them outside is a desolate landscape of utter ruin as far as the eye can see. What could have caused such destruction? A natural disaster? A nuclear catastrophe? A time slip? With mixed emotions of hope and despair, the survivors journey towards Tokyo, encountering other survivors and inevitable chaos throughout their shattered world.