You need to drive 1 km in reverse at 100+ km/h.
Buy the Nissan Skyline GT-R V-Spec II (BNR34) and only need the Lv. 1 Transmission upgrade. Tune the final gear to the lowest setting (2.545).
Load up to any straight, U-turn and go reverse at 100+ km/h. Should unlock after passing 1.1 km.