Story
In April 1999, Jotaro Kujo travels to a town in Japan called Morioh to find a young man named Josuke Higashikata, the secret love child of his grandfather, Joseph Joestar. Upon finding him, Jotaro is surprised to learn that Josuke also possesses a Stand. After their strange meeting, the pair team up to investigate the town’s proliferation of unusual Stands!
Synopsis via AniList (English).
Preview
From the anime adaptation: JoJo's Bizarre Adventure: Diamond is Unbreakable.