Pyrasia is a wanted thief who joins up with the Assassins after her house is burnt and her father is murdered unjustly by the corrupted royal guards. Then she finds out that all the corruption started years ago when a group of twisted nobles made contracts with Demons for power, and took over the throne of the kingdom. In order to gain power strong enough to fight off the Evil, Pyrasia and the Assassins make themselves contracts with different Demons to reclaim the throne.

Lore:

Half-Demon, in this case, doesn't mean a child born of Human and Demon. No. Half-Demon here means a Human who makes a contract with a Demon, giving something of importance to the Demon, and receive something back in return. Demons, however, have no need for jewels or money, they usually ask for the Human's Soul. Some Demons, however, might prefer something else, such as Joy, Blood, Heart, or even Love, so to speak. While what Human usually ask for is Power or Knowledge.