Half a year has passed. Arriving in the Iron Fortress, Ikoma and Mumei set foot in Unato: another ravaged zone that fell into the grip of the deadly Kabane. In this war-torn zone, the group fends off more dangerous Kabane that are attacking with patterns they had never seen before. The Iron Fortress crew eventually meet up with a survival group which requests their aid in reclaiming the zone. The newly forged alliance ventures deeper into the area of the castle and investigates the peculiar case of these new Kabane. But their search for answers unearths truths that are far more horrifying than they imagined. Forced to confront the reality behind the Kabane, Ikoma, Mumei, and their allies come to realize the despair buried within Unato.

Compilation film of the second half of the TV series.

During an era of rapid industrial growth, humanity is beset by the emergence of a mysterious virus, capable of turning humans into mindless creatures called "Kabane." With a desire for nothing but human flesh, these undead beings can only be killed by destroying their hearts—which are encased in a cage of unyielding iron. Faced with such a dire situation, the surviving population has retreated into fortified cities known as "Stations." Isolated from the surroundings by massive moats and towering walls, the only contact with the outside world and other Stations is via a drawbridge for armored "Hayajiro" trains. At Aragane Station, Ikoma works as a steamsmith to maintain the city's active transportation. Despite his role, he is angered by mankind's cowardice and inability to repel the Kabane. Utilizing his free time and knowledge as an engineer, Ikoma has created a new weapon to ward off the horde. An opportunity to test it presents itself when the Kabane invade Aragane Station, yet this encounter will prove to be much more than just a trial run for Ikoma.

When highly evolved AIs set out to eradicate mankind, the carnage that ensues fills the air with the stench of fresh blood and burning bodies. In a desperate bid to prevent the calamity from ever occurring, a scientist bets everything on a remnant from the past. Turning the clock back a hundred years, AIs are already an integral part of human society, programmed with specific missions meant to be carried out for their entire course of operation. Vivy, the first ever autonomous AI, is a songstress tasked with spreading happiness through her voice. In a theme park where she hardly ever gets a proper audience, she strives to pour her heart out into her performances, bound to repeat it day after day—that is, until an advanced AI from the future appears before her and enlists her help in stopping a devastating war a hundred years in the making. With no time to process the revelation that flips her world upside down, Vivy is catapulted into a century-long journey to avert the violent history yet to come.