History
Josuke apparently developed his stand off-screen in the events of Part III, when Jotaro Kujo and company traveled to Egypt to kill Dio Brando. As a result of Dio being pierced by the stand-creating Arrow, Josuke, possessing the Joestar Bloodline that runs in Jonathan's body, develops a stand, but suffers a fever not unlike that of his half-sister Holly. He is then saved by a then-high school student with a pompadour, who throws his coat under his mother's car in order to allow their car to plow safely through the snow. This then inspires Josuke's admiration for the man with the pompadour.
Diamond is Unbreakable (1999)
Eventually, however, a serial killer comes into the scene, and Rohan Kishibe and Koichi Hirose's encounters with the ghost of his first victim Reimi Sugimoto forces Josuke to gather the stand users he's encountered thus far and warn them of the killer.
After he defeats Angelo, he finds himself approached by his nephew Jotaro who explains to him about stands and the Arrow which is the catalyst of stands.
He finds out that a man in possession of the arrow has been creating the stand users and goes on to finds him and his brother. The elder Nijimura explains that he made stand users in order to find one suitable enough to destroy his father who's mutated. Before Keiicho can further explain, he's killed by Red Hot Chili Pepper. Okayasu vows revenge by staying with Josuke.
He soon finds himself being attacked by other stand users on the way to Kira (who changes his identity) before finally witnessing his defeat.
JoJoLion (2011 alternate universe)
Josuke has been shown to have at least one alternate counterpart in the town of Morioh. The first, and most apparent, is the protagonist of Part VIII, who takes up the name written with a different kanji. The second is shown to be the current patriarch of the Higashikata family, Norisuke IV, whose birth name was shown in a family tree to have been "Josuke".