American transit Youtubers often portray Japan as some kind of mass transit / train based utopia but this is patently false. Even though Japan has high population density and expensive gasoline, it still takes significant political willpower to construct high speed rail, local rail, and fight against car-based infrastructure.
Examples
By definition, if you take the train when visiting Japan, you cannot see the car dependent suburban development. Since these new developments have no "culture" (i.e. shrines and shit) nobody goes out of their way to visit them
Medium sized cities with no strong incentives for extremely high density city structure tend to build these suburbs (Nagoya, Gifu, Kobe, etc)
Rural areas are car dependent too and have strip malls and unwalkable towns. Especially visible in Kyushu and Shikoku
Even places like Tokyo exurbs in Nagano can be quite car dependent with poor infrastructure for biking
The Kyushu Shinkansen does not go through Saga City / Prefecture. Riders taking the Shinkansen from Nagasaki to Fukuoka have to transfer to low speed rail.
The reason appears to be NIMBYism from Saga residents, who would have to partially pay for construction yet would see no significant decrease in travel time to Nagasaki or Fukuoka (i.e. this only benefits Nagasaki and Fukuoka residents) [citation needed]
Okinawa has limited mass transit despite very high population density and traffic congestion. Sounds similar to Hawaii