Adonis Johnson, the illegitimate son of the late heavyweight champion Apollo Creed, struggles with his identity and purpose. Despite being raised in affluence after being adopted by Apollo's widow, Mary Anne, Adonis' deep-seated need to forge his legacy drives him to pursue professional boxing. He harbors a relentless determination to not be defined by his father's name, seeking to make his own mark in the boxing world. Fueled by this ambition, Adonis quits his job and moves to Philadelphia, intent on tracking down his father's old friend and rival, Rocky Balboa, to ask him to become his trainer.

Initially, Rocky is reluctant to re-enter the boxing world he has left behind but is eventually swayed by Adonis' passion and resemblance to his old opponent and friend. As Rocky takes Adonis under his wing, the young fighter must tackle the challenges of an unrelenting sport while dealing with his personal demons and quest for identity. The duo embarks on a journey that brings back memories from Rocky's past and pushes Adonis to confront his heritage. Training starts for Adonis, and with it, a test of endurance, as he works to earn his place in the boxing hierarchy and establish who he wants to be both in and out of the ring.