Yuusha-chan no Bouken wa Owatteshimatta

This is an anime adaptation of the Doujinshi of Yajirushi Key.

After terracing the Demon King and brought peace to the world, the heroine’s mission is to exterminate the last members of the army of Demon King. However, every night she has nightmares in which demons beat her and abuse her. Even though the heroine knows that it is only nightmares, her whole body feels the sensations of the acts she undergoes in her dreams, which mentally exhausts her.

One day, the heroine eventually discovers the source of his nightmares, but it is already too late to resist.