Hakoniwa no Fräulein
箱庭の令嬢探偵〈フロイライン〉
The story revolves around supernatural-loving high-schooler Akira Satou, who hears of the existence of an agency that will solve all cases not of this world. When he arrives at the agency, however, he encounters high-class lady Yui Mikami and her butler Koushirou Kujou, who is only kind to her exclusively. They may not look like detectives, but strange incidents await them.
(Source: ANN)