In a world surrounded by toxic gases and hazardous wastes, the twelve cities that built on the top of the highest mountains have managed to create "safe zones" in the world and used the people they placed in these safe zones to raise their civilization. The brutality of these twelve city created a  rebellion and gave birth to a new powerful kingdom. Twelve cities were desperate in the face of the new Hildeswat Kingdom. Cities lost their former glory and began to be destroyed one by one by Hildeswat.

Octavia Tarquinia was the princess of one of the last three cities among the clouds. The life of Octavia, who has isolated herself from everyone and spends her days in a dilapidated library, is turned upside down when her city was also occupied.

Octavia was the only person left.

After Octavia came across with Maksymilian Friedrich von Vogel, who was on officer that part of the army which occupied her city, her endless fall has begun.