Jonathan Joestar is an aristocratic boy whose life is suddenly turned upside down by a mysterious new boy who arrives, Dio Brando. Dio has a connection to his father, and over time, a rivalry forms as Dio becomes obsessed with a mysterious, ancient, and mystical stone mask that Jonathan's father keeps.

(Source: Lost Media Wiki)

Notes:
- This entry is for the 2007 movie, not to be confused by the first arc of the 2012 TV anime adaptation of JoJo's Bizarre Adventure, also named Phantom Blood. Nor the movie format 're-edit' of said first season compiled from the 2012 TV episodes.
- This film hasn't been released publicly outside of its original limited theatrical run and is considered mostly lost, apart from several trailers and a found 16-minute undubbed clip compilation used for a student sound design assignment.