Import Tuner Challenge is set on the Shuto Expressways of Tokyo, Japan. There a total of 415 rivals in the game. It features C1 and Shinkanjo like many other TXR games but unlike TXR3, Import Tuner Challenge does not feature the highways of Nagoya, Osaka, and Yokohama. But two new highway sections of Tokyo are in the game which are Rt. 3 Shibuya and Rt. 4 Shinjuku.

After the 13 Devils have been defeated once more in the Kaido Circuit, Motoya Iwasaki, aka Speed King, disappeared suddenly, leaving without a trace. Since then, many drivers from all the Japan come to Tokyo in order to have his title of "Speed King". The hero here is the best friend of Iwasaki and beats Bloodhound, Midnight Cinderella, Platinium Prince, Skull Bullet's gang & eventually, the Phantom 9. In the meantime, Bloodhound reveals to the racer why Iwasaki has been depressed for a long time : his girlfriend died because she was ill and Iwasaki wasn't there to support her.