Jotaro Fukamachi is a private detective. Divorced with a woman he can not forget, with whom he had a daughter. He has a reputation for sleuthing, but it is rather stingy and often shows interest. On the other hand, he has principles (sometimes quite caricatured) which it stands. The main one being "always keep a promise," even if the person to whom he made this promise is not of this world. Suddenly, he happens to invest excessively in matters that he won't get any profit.