Student or Learner
Tokyo is the city of the largest in Japan.
is it grammatical?
No, it's the largest city.
You can say it's the city with the largest [something], but not simply the largest.
Detroit is the city with the largest percentage of American-made cars.
New York is the city with largest immigrant population.
Paris is the city with the largest number of chocolate croissant lovers.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.