Project Justice for the Dreamcast is basically a sequel to the PlayStation's Rival Schools, which also originated in the arcade before moving to a home console. Players take on the role of a student at one of several adversarial high schools. The student's appearance and abilities are related to the school she attends, as characters from the athletically oriented school may attack with sporting equipment while kids from the more intellectual academy might use a blinding flash camera or swing a band instrument at opponents. The fighters in Project Justice are humorous caricatures based on familiar high school stereotypes.
As in Rival Schools, Project Justice players have the option to use a "Team-Up" attack in which two characters on the same school team assault an opponent at the same time, using outrageous moves and inflicting extra damage. Project Justice allows a counter attack for these team ups, however, so the move must be used skillfully. Also new in this edition of the series is the "Party-Up" move, in which all three members of a school team attack together. This option can dish out a massive amount of damage and often features entertaining animations, but is also costly to the attacker's "Super Meter" energy reserve and must be used sparingly.