Ai ga Tamesareru Shiro

Sara is hired to work on remodeling the interior of a castle, so she goes off to the Dukedom of Illyria. The Prince of Illyria, Gabe, was once Sara's fiance. But when the family treasure that Gabe lent to her went missing, he accused her of being the thief and canceled their engagement. Sara thought that there'd never be another chance for a mere interior designer like her to meet a prince, but Gabe is waiting for her in Illyria, and he hasn't forgotten a thing. He looks at her coldly and declares that she won't leave his castle until she returns the "stolen" necklace!