Giving rise to the modern age, undead monsters called Kabane suddenly started appearing. One bite is fatal, but then the victim will come back to life as one of the creatures and proceed to attack its former fellow humans. The only way to destroy them is by piercing their hearts.
People have constructed fortresses called "stations" throughout the land in order to deal with the Kabane threat and have somehow survived by shutting themselves away. Only armored steam locomotives nicknamed Hayajiro can travel from station to station.
Ikoma is a young steam blacksmith who lives at one of the stations. He independently develops a "piercing gun" that can kill the Kabane.
One night an out-of-control Hayajiro crashes through a station where Ikoma lives. All of the crew members were wiped out and resurrected as Kabane!
As the Kabane overrun the station, Ikoma runs against the stream of panicked people. "I won't run away this time! I'll kill the Kabane with my piercing gun!"
And so Ikoma's battle for the sake of glory begins...