Set in 2001, two years after the events of "Diamond is Unbreakable," Koichi Hirose is sent to Italy and tasked by Jotaro Kujo to search for Giorno Giovanna, an aspiring mafia gangster who is a son of Dio Brando. But as Dio possessed the body of Jonathan Joestar at time of his conception, Giorno is technically a Joestar and takes more after them than the father he never knew. The series follows Giorno as he joins the mafia organization Passione, moving up through its ranks with the intention of becoming its boss to improve life in Italy.