Princess Principal

The setting of Princess Principal is Albion, a made-up version of Britain. The Kingdom of Albion monopolized a strange mineral known as "Cavorite" in the early 20th century to create a fleet of heavily armed airships that elevated Albion to the position of world dominance. The "London Revolution" was an effort by the lower classes to topple the royal family when the proletariat of Albion became enraged at the ruling class for mostly disregarding their situation. The conflict eventually came to a standstill, and Albion was divided into the Commonwealth and the Kingdom by a massive wall that was built across the heart of London.