From my understanding, throughout the whole anime series, the touge rules has been one of the following:
Cat and Mouse/Sudden Death (using Wikipedia Tōge terminology...)
- Cars start bumper to bumper, if cat finishes a round ahead of the rat with a considerable time difference, cat wins. If rat overtakes the cat, rat wins. If neither happen, proceed to a new round and swap positions.
- Example: When Keisuke beat Wataru on Shomaru pass
- Cars start side by side (or rolling start up to first turn), whoever is leader at the end wins.
- Example: When Takumi raced Keisuke at Akina pass
When Project D raced Purple Shadow, both Takumi and Keisuke's races started bumper to bumper indicating that it wasn't grip gambler. However, in both cases, they were overtaken at one point and the race didn't end, meaning it wasn't cat and mouse sudden death. Perhaps there's a non-sudden death version of cat and mouse, which would make a lot more sense as both races went into multiple rounds.
However, there is still something not quite right. In Takumi's case, he overtook his opponent back and prolonged the race. In Keisuke's case, he overtook his opponent back and the race ended (with no noticeable winning distance).
What was different between Keisuke and Takumi's race so that Keisuke won? Keisuke regained his lead but that should have taken it into the next round. Even Keisuke himself said "That felt kind of questionable. Want to go for a third run?"
So overall, I am beyond confused. Exactly what Touge race rules did they race in?