Go Hibiki, known as Speed Racer, is Kenichi Hibiki’s younger brother. Kenichi, a racing driver and motor engineer, was presumed dead after an accident during a test drive of the Mach 5’s experimental "X" engine. Their father, Daisuke Hibiki, salvaged the wrecked vehicle and rebuilt it as the new Mach 5, integrating the surviving "X" engine and a driver-protection system called "Safety Seven." To honor his brother’s legacy, Go races the Mach 5 in the Grand Prix with ambitions of becoming a top racer. His family includes father Daisuke (Pops), mother Misuzu (Mom), and brother Kenichi (Rex). Reporter Trixie befriends Go during his journey. Spritle, reconceived as Trixie’s younger brother, is frequently accompanied by a chimpanzee named Rocky. Sparky maintains the Mach 5 as its mechanic. The series’ narrative shifts significantly midway: initial circuit racing gives way to science fiction when the Mach 5 hits 555 km/h, activating the "Mirage Shot." This transports Go and his companions to the year 2555, where they battle an alien tyrant named Handler. Their mission focuses on securing the Ezekiel Wheel, a potent energy source, to defeat Handler. This transition redirects the storyline from traditional racing.