England, 1868: a thief comes across the site of a carriage accident that claimed the life of one passenger. While rummaging through the wreckage for valuables, he finds a peculiar stone mask. Suddenly, one of the passengers, an aristocrat, regains consciousness. He sees the thief and mistakenly believes him to have saved his life, as well as his infant son. The thief plays along with the aristocrat's misconceptions and the two men introduce themselves to each other: the aristocrat, George Joestar; and the thief, Dario Brando.
Both men are fathers whose sons grow up in vastly different backgrounds. George's son, Jonathan Joestar, known affectionately as "Jojo", grows to be a considerate young boy, at times hot-tempered, but always striving to be a gentleman. Dario's son, Dio Brando, grows into a callous and disenfranchised youth, doing what he can just to survive.
One day, twelve years later, Dario takes deathly ill. On his deathbed, he begs his son, Dio, to go to the Joestar manor. Because George mistakenly believes he owes a debt to Dario, he would have no reservations with taken Dio into his home. Afterwards, he wants Dio to do what he can to make the Joestar family's fortune his own. While Dio has no love for his abusive drunkard father, he nonetheless agrees to follow through with this plot, if for no one's sake other than his own.
The next day, Dio arrives at the Joestar manor, where he is greeted by Jonathan. When Jonathan's dog, Danny, appears, Dio thoughtlessly kicks him, shocking Jonathan. Dio is able to evade suspicion by explaining that Danny startled him. George welcomes Dio into his home and adopts him as a son.
Once welcomed into the Joestar family, Dio sets about destroying Jonathan's social life, winning his father's favor and isolating him from his friends with vicious rumors. Jonathan, however, finds solace in his growing friendship with a young girl, Erina Pendleton, whom he rescued from bullies a few days prior. When Dio realizes Jonathan and Erina hold a flame for each other, he decides to throw a wedge between them by stealing Erina's first kiss. This leaves Erina so ashamed that she cannot bear to face Jonathan again.
When Jonathan realizes what happened, he confronts Dio. The two get into a brutal fist fight with one another. At first, Dio manages to gain the upper-hand on Jonathan using dirty tricks, but Jonathan's rage and determination allow him to land a powerful blow to Dio's face, drawing blood that splashes on the Joestar family's stone mask and causes it to protrude spiky tendrils. As Dio, his pride as wounded as his face, prepares to stab Jonathan, George puts their fight to a halt and sends both boys to their rooms.
Dio, however, cannot let the slight Jonathan paid unto him go unanswered. That evening, he gets his retribution by locking Jonathan's beloved dog Danny in an incinerator. As Jonathan becomes so fearful of Dio that he can no longer muster the courage to confront him, Dio realizes that he may have underestimated Jonathan. If he is to take the Joestars' fortune, he would need to rethink his strategy...