The Tokyo Challenge is a separate part of Midnight Club 3: DUB Edition Remix.
One can select the Tokyo Challenge from the main menu at any stage in their career, and can use any unlocked cars in the career mode, or start the Tokyo Challenge without starting career mode in the first place. The player does not have to finish the Tokyo Challenge to enter career mode or vice versa, however, the player must unlock the Cadillac Cien, Kawasaki Ninja ZX-12R or the Class A Vehicles to finish the Tokyo Challenge.
There is one tournament for each type of club, whether it is Luxury Rollers, By Invitation Only, or Choppers Of America Bike Club, there is a tournament for each. Each Club Tournament consists of 3 races, and winning the tournament unlocks a car of that type, for example if you win By Invitation Only you will get an Exotic car. These are marked as blue trophies on the Tokyo Free Roam Map, or grey if you are not driving the right car/bike of the club.
There are 4 Class Tournaments in the Tokyo Challenge, one for each class of cars (Class D, Class C, Class B, Class A). If you win the tournament you will get the same class car as the tournament, for example, if you win the Class D Tournament, you will get a Class D. These are marked as white trophies on the Tokyo Free Roam Map, or grey if you are not driving the right car class.
Tournaments are unlocked by completing Tokyo Challenge Races, marked as purple diamonds on the Tokyo Free Roam Map. The more Tokyo Challenge Races you win, the more tournaments you will unlock. When you unlock all the tournaments in Tokyo, Tokyo Challenge Races will turn into regular City Races. The races can be Ordered Races, Circuit Races or Unordered Races.