Yuusha-chan no Bouken wa Owatteshimatta!

The heroine who defeated the Demon King and brought peace to the world has become arrogant. She now easily defeats the remnants of the Demon King's army but can no longer level up. However, she has disturbing dreams in which she is defeated and violated by demons, feeling such real pleasure that it wears down her mind. She discovers the source of these nightmares, but it is too late to resist. Each night, these dreams corrupt her further.