A dead man's car wins races because his father refused to let it stay broken. Speed Racer X treats every victory like a conversation between a son and the father who kept his memory running. The Mach isn't just fast, it's a monument that moves, and every lap is a lap the original driver never got to finish.

Kenichi Hibiki, a racing driver and motor engineer, develops a new engine called X and builds the Mach around it, but a test run before the car is finished ends in a crash, and Kenichi is judged dead. His father Daisuke, who watched the whole test, recovers the wreck as a keepsake of his son. Years later Daisuke rebuilds it into a new Mach, keeping the X engine, which came through the crash intact, and adding Safety Seven, a set of seven protective devices meant to keep the driver safe. Behind the wheel now is Go, Kenichi's younger brother, set on carrying on his brother's will. Go enters the Grand Prix and steadily grows into one of the world's top racers in this sci-fi action sports series.