Immortal Brave

There was once a demon king which threatened humanity, and plotted to put the world under the control of the demons. He was defeated by the one and only princess hero Eclair. Two years after the defeat of the demon king, peace was restored to the world, but the whereabouts of the princess hero is unknown. A young man Frey, hired as a servant in a certain mansion with the promise of high pay, meets the princess hero Eclair, who was under house arrest. For some reason, she is suffering from an impulse that makes her want to kill demons when she senses their presence. Just what secrets do the princess hero, her father, and the maid Tia hold-- [Translated from NovelGame]