I was in Japan for a couple months, more than typical tourists. And I understand it can be confusing as to where to find your favourite sports or places to exercise. Here are my recommendation, based on the type of exercise.
- on the streets
The most convenient answer is obviously just on the street! Even in the city area, you can often find alleyways with no traffic light stopping you every couple hundreds meters
2. By the River
Most of the major city in Japan should have a river or waterfront. And there are usually nice walkway that provides undisruptive experience while letting you enjoy the scenery. Sometimes you might also see youth baseball team practicing on a weekend morning!
3. in the park
There are also usually some parks, vary in size. You will find the park a lot more lively compared to other choices.
I will put in more if I can remember. But these are my usual go to places when I want to get a run in. Please let me know what your experience is like!