Comic Master J

In the manga industry, there is a legend: If you leave a message on a bulletin board at a Shibuya train station, you can obtain the services of a certain man: Comic Master J, an assistant mangaka who can instantly complete any publication manuscript in any art style for the price of 5 million yen. However, he refuses to work on manga without a "soul." But what is J's true identity? Why does he wear an overcoat lined with pens and rulers? And for what reason does a man of such artistic talent choose to live in the shadows of the industry, rather than working on a manga of his own creation?