It is the Warring States period in Japan. After the passing of Hideyoshi Toyotomi, many warlords started to watch for a chance to be the next ruler of the land. In the midst of time where history is changing with the upcoming battle of Sekigahara where the major daimyos split into Eastern and Western Armies, aiming to fight a decisive battle, there were demons who lived in the shadows of history, avoiding human involvement.
Our protagonist is a member of the Ten-Demon Alliance, a coalition of demon clan chieftains. Her duty is to protect Princess Yase, leader of the Ten-Demon Alliance. One day, Princess Yase summons all the Ten-Demon Alliance chieftains across the land. They are delighted at the reunion, but shortly after that, Princess Yase is attacked by forces unknowns. She is greatly weakened and falls into a deep sleep. The Ten-Demon Alliance chieftains, including the heroine, seek out the perpetrators who attacked the Princess. However, it becomes evident that within comrades which were believed to be tied with a strong bond, there were demons secretly in league with humans violating the commandment which all demons must obey.
The protagonist's mission: to find a way to rouse the Princess from her slumber, and end demon interference with human affairs. This is the story of the demons who ran through the Warring STates period, with the heroine having two missions in her mind.