SERIES 4: "Diamond is Unbreakable" The fourth arc of Jojo's Bizarre Adventure, Diamond is Unbreakable, follows Josuke Higashikata and his good friend Koichi Hirose as they protect their town from the influx of Stand users. Joseph Joestar and Jotaro Kujo arrive to warn Josuke about the Bow and Arrow one of Dio's henchmen uses to bring out a person's Stand abilities, but it is up to Josuke, Koichi and their allies to defeat those who would use their Stand abilities for evil, most notably Yoshikage Kira.