October, 1987, Autumn. In Suganami, Tokyo, there lives the Kinoshita family whereby the father draws very little pay out of his job as an ordinary salaryman. In order to cover expenses, he decides to let out the second floor of their apartment to earn additional rental income. One day, an obstinate-looking eldery dog, accompanied by a younger boy-dog, came knocking on their doors. The eldery dog addresses himself as Norayama Kuroyoshi and introduces his grandson as Norakuro. The former wants to open a detective agency and intends to rent the unit for their office. He will be the president of the investigative bureau while Norakuro-kun will be the director. He will also recruit one of the Kinoshita's sons, Keita-kun, as his employee and their advisor will be the girl-next-door, a high school student by the name of Rika Sawaguchi. On the third day since the official opening of the office, the telephone rang, a signal of a new case.