百機夜行（Hyakki Yakou）

19th to Early 20th Century

An era in which territorial expansion was carried out around the world according to the rules of the great powers. The Great Empire of Ivan (I-koku), the most heavily armed nation, and the Mizuho Imperial State (Kōkoku), the protagonist’s homeland, went to war. The Imperial State, still in its early stages and a small country, was rushing to build up its military for self-defence when this conflict erupted.

As a result, the Mizuho fleet was defeated in the initial engagement, leaving the army isolated at Ryōjun Fortress. The I-koku forces then launched a landing on the Imperial State’s homeland.

On the brink of collapse, the Mizuho Imperial State was saved in the homeland defence battle by the six military clans known as the Rokukyō Families, long rooted in the nation as a warrior aristocracy, and by the Walking Armours developed within the state itself.

The story begins three years later in the Mizuho Imperial State.

Note: The Walking Armours would later evolve into Walking Tanks, which became the standard weapon worldwide.

[From official website]