Wolf Kanagushi

He was an up-and-coming bantamweight boxer. In order to get recognition quickly, Joe targeted the bantamweight rookie champion. Wolf was a confident and brash fighter who was easily provoked by Joe into a fist fight, ending in a double knockout.
This news eventually led to the public demanding a match between them, which Wolf lost.

He eventually became a thug who got defeated due to his weak jaw, and later borrowed money from Joe after rekindling their friendship. By the end of the series he finally pays it back and supports Joe for his last match, actively cheering.