THEY WALK!!
Anyone that has ever been there can tell you how much walking you’ll do. The train system is the primary means of travel so even if you travel a fair distance using them you must still walk to/from the stations and getting to your final destination. Taxi’s are *very* expensive.
Tokyo is built upward, not outward like the USA. One of the consequences of having so much land in this country is that we’re very spread apart, even a grocery store requires a drive for most. This all results with very little walking. Now we even shop online, rarely going to malls - which at least got us walking around.
Walking...it’s the best exercise you can do.
I walk at least 5 miles/day on a treadmill at 12 degree incline. Hope that counts.