His Majesty the Demon King's Housekeeper Vol. 6 (manga)

For Takatsuki Sakura, a trip to the library turns into a fantastical journey. She has been swept away to a grandiose castle ruled by a gorgeous demon king. Magic and wonder covers every room. Taking it in, Sakura can hardly breathe… because of all the dust and dirt. A curse has prevented this kingdom from cleaning. Only Sakura and her housekeeping knowhow can scrub away this dark magic grime!