Doc

A doctor who runs the Hanazono clinic, and looks after most of the underworld denizens of Shinjuku. As a result, he does not make much money out of this venture and occasionally doubles as a club harker in order to make ends meet. Despite this, he is a very capable doctor. He is the second person after Umibozu to realize that Kaori has returned in Xiang-Ying. In fact, before hiring Tomoko as his nurse, he had previously employed Kaori when she was around Xiang-Ying's age.
This "Doc" is based on the original Doc in the City Hunter manga where he helps Ryo out on a consistent basis. "Doc" did not appear in the City Hunter anime series, so therefore viewers may be confused as to how Ryo is associated with him.

(Source: Wikipedia)