Kabaneri of the Iron Fortress Movie: Burning Life

A mysterious virus appears during the Industrial Revolution that transforms infected humans into Kabane and rapidly spreads. Kabane are aggressive, undead creatures that cannot be defeated unless the glowing golden heart, which is protected by a layer of iron, is pierced, or an important body part is completely severed. However, most melee weapons and the steam-pressure guns used by the bushi are not very effective against them so they fight them using powerful armored trains (Compilation film of the second half of the original TV series.)