While looking for a ghost that helped him as a child, Satou Akira has run into a fair amount of spirits that he doesn't even see. One day, he goes to a supernatural detective agency for help, and he meets the adorable Yui and her devoted butler Kujou. Using her power, Yui ends up helping him with a number of the dangerous supernatural troubles he gets himself into. Akira starts to feel attached to the detective agency, and wants to learn more about the supernatural! (Source: MangaHelpers)

My lady. I have prepared delicious black tea with cakes and outstanding mysteries. What's Hakoniwa Detective Agency? It is a detective agency that handles extraordinary cases. It accepts cases that are related to the supernatural, urban legends, or rumors that people do not consult with common detective agencies. It also provides delicious black tea and desserts to our clients. Koushirou Kujou He is the butler of Hakoniwa Detective Agency, but is also a famous detective. He is not only erudite, but also insightful with eloquence. He is overprotective of Yui, but is very invective to Akira. Yui Mikami She appears to be a petite girl; however, she is able to see and be possessed by spirits. She is the master of Hakoniwa Detective Agency. She is fond of desserts. Akira Satou He is searching for "the phantom of that day" which stayed by him at a time when he was distressed. He is a high schooler finally arriving at Hakoniwa Detective Agency. He has a positive way of thinking and is resilient.