This is a pocket-sized Manga series featuring the 13-year old Ken Nishikagi, who is an intelligent and efficient teenager spending much of his time trying to solve diverse types of crimes in Tokyo. This is done in the spirit of his great ideal Sherlock Holmes, whose surname he also uses as an alias.
To help him he has the same aged girl Mako Kitahara (alias Marble) and the younger Asashi Kogoro. They also have good and fruitful connections with the Tokyo police mostly represented by commissioner Harada.