End of the 19th century ~ beginning of the 20th century. the world is undergoing territorial expansion according to the rules of the great powers. Ivan the Terrible leading the most well-equipped empire in the world wages war on the Imperial Kingdom. The Imperial Kingdom still in its infancy is in a hurry to secure military strength for self-defense. As a result, in the first battle, the Mizuho Fleet was defeated. The army was weakened, and invasion on the mainland of the Empire began. What saved the empire, which had become desolate, during the mainland defense battle was the existence of the “Six families,” six military clans that had long been rooted in the Empire as warrior families, and the “Walking Armor,” which had also been developed in the Empire. The story begins three years later in the Imperial Kingdom of Mizuho. The “walking armor” was later transformed into the “walking tank,” which became the world's standard weapon. [From official site]