Ashita no Joe
Ashita no Joe tells the tale of a wandering orphan named Joe Yabuki. He falls into one of Tokyo's slums and gets into a fight with a local gang and his street fighting skills gets him the attention of a washed up alcoholic boxing trainer. Until he sticks up for Joe when the gang comes back to finish Joe, Joe decides to live with the trainer. Despite the trainer's generosity, Joe is still committing money making scams and lands him in prison. While serving time, he meets another boxer named Rikiishi Tooru who gets Joe interested in boxing. Upon release, Joe then pursues a boxing career.
(Source: Anime News Network)