Hime to Majin to Koi Suru Tamashii

During the Heian Era, the queen of the demon world sent her two daughters Kaguya and Sakuya to the human world for training, with the one with better results becoming the successor to the throne. Kaguya used her power to make humans suffer, while Sakuya blended in with the humans to control them from within. However, Sakuya fell in love with an onmyouji and thought that living in the human world isn’t that bad. She then received a request: to eliminate her older sister Kaguya. With the help of her lover, she successfully sealed Kaguya and brought peace to the land. However, her lover soon passed away due to illness and she returned to the demon world. Thousands of years later, Sakuya will be crowned the new queen, but she must marry someone. There is only one person in her heart, so she heads back to the human world to seek her reborn lover.