Passenger cars need to go for inspection and registration/road fees every 2 years called the Shaken, which is quite expensive ~over $1000. That's why you see mostly imported cars at the 5 year mark (initial Shaken is @ 3 years). Then every 2 years thereafter.

The Japanese tend to take pride in car ownership, as not everyone can buy one, they need to prove that they have parking space at home. Most commute a very short distance to work, or sometimes just a weekend car. So there are actually very good examples available if you want to pick up a low mileage classic car from Japan.