The Duke's Maid

The princess of the kingdom of Elverne, who became the sacrifice of the Demon King Seal, Serenian, woke up 300 years later, in the northern part of the continent. She wants to make a new living as a commoner, named Serena, and applies to the rumored Duke of Valois as a maid. There, she meets the prickly but cute Yubel and Kairos, the Duke of Valois, known as the "Killer of the Battlefield"...?!