???/Unknown is the canonical final boss in the Tokyo Xtreme Racer Series; in every game of the series to date and drives a Datsun Z based on the "Devil Z" from Wangan Midnight (except in Tokyo Xtreme Racer 3). Unknown goes by ??? in both Tokyo Xtreme Racer: Zero and Import Tuner Challenge.
"The outside looks classic, but the inside is completely different. Powerful acceleration and out of line turning ability are adequate for the legend"
"Legendary racer completely shrouded in mystery. Nobody has ever actually met him. Rumored to appear when there is another racer like him."
??? accelerates much faster than both Speed King and White Charisma to 263 mph, to the point where even using a top-tier car is near hopeless if challenged on the Wangan (assuming the AI doesn't make a mistake). Fortunately, the AI itself has trouble controlling the over-steer prone handling of the car; suggesting that the best strategy is to manipulate a race start in the Kanjo loop. ??? will eventually make a mistake, allowing the player to secure a relatively easy victory.
He drives a Datsun 240z in Tokyo Xtreme Racer: Zero (code-name Type-S30ZX in the game - Class A).
In Tokyo Xtreme Racer: Zero, he drives a dark blue Datsun 240Z, an obvious reference to the "Devil Z," the lead car in the popular "Wangan Midnight" series. His driving skills and car power are very high compared to the other bosses. It is hinted that the driver may be Akio Asakura, the driver of the car from his respective series.
In Tokyo Xtreme Racer 3, Unknown returns and requests the battle after the player has defeated all 599 rivals. His appearance is a ghosted, transparent version of your current vehicle. He can go through traffic cars, as well your car (i.e. blocking won't work). Unknown however won't have the engine swapped and will use the original car's engine, to the player's possible advantage.)
In Tokyo Xtreme Racer: Drift 2, one of the rivals resembles Unknown, although Unknown himself did not appear in the game. The last boss goes to Emotional King.
In Import Tuner Challenge (Shutokou Battle X), ??? returns as the final boss and as the dark blue Datsun 240Z S30 after the player has defeated all the rivals.