Hoshinokuni, a country with a history of 300 years, has had an inherited contract since its foundation. For generations, a priestess from the People of the Shadow Guardian, a minority tribe in the east with unique powers, was to be the empress of the country. However, half a year after Somali, a priestess in love with the new emperor Eigaku, is made empress, the contract is broken in the worst possible way. To avenge her sisters death, her younger sister Kukuna sneaks into the back palace as a courtesan, but the beautiful prince Baekyu takes a liking to her. A girl with a beast in her heart hunts beasts in human skin in this epic tale of revenge in the Chinese imperial palace.