The title character of Kafka's story is clearly the protagonist. The story tracks the hunger artist's development as his fame waxes and wanes.
The protagonist has a love/hate relationship with his audience. On the one hand, he despises their lack of taste and appreciation for the finer points of his artistry. On the other hand, as the story tells us, the audience is his reason for existence: what's a performer without anyone to perform for? Not much, as we see when his audiences stop coming.
The manager is a problematic guide for the protagonist. He promotes the artist's career and manages the more theatrical elements of the artist's performance to keep the crowds coming. But the manager is mostly interested in the act continues to make a profit. This motive conflicts with the artist's desire to become the greatest hunger artist of all time.
When the hunger artist dies, a young panther replaces him in his cage. By using an animal as a foil, the story poses some interesting questions: Are the artist's performance and the panther's really so different from each other? How different are the human and the animal?