During the industrial revolution, a virus caused the emergence of monstrous creatures dubbed "Kabane" that preyed on humanity. These beasts boasted indestructible steel-coated hearts, making killing them nearly impossible. To make matters worse, if a Kabane bit a human, the victim would become one of them. Against all odds, fortified civilizations like Hinomoto Island stood strong, safeguarded by a towering wall from the relentless hordes of Kabane. To transport people safely into the walled city, heavily-armored trains were constructed by young men such as Ikoma. Due to his exceptional skills, Ikoma succeeded in creating a potent weapon that could destroy Kabane, eagerly awaiting the chance to use it in battle. Unbeknownst to him, his opportunity to do so came far sooner than anticipated.