Mico Is the "Human" Detective

London, the city where humans and non-humans reside. Serizawa Mico is a girl with the ability to see things that are not human. In place of her late grandfather who possessed the same ability, she travels to London, determined to help others. Starting from Bill, a man who owns a detective agency and was once her grandfather's partner, what changes are there in store for Mico as many other encounters await her?