In general, yes, kids are taught to be responsible for cleaning up, not littering, etc. from an early age. Of course people do litter but I think it's much less than in some other places.Why Japan is a clean country? Is it thought since elementary the habits of cleanliness?
In Paris 30 years ago they had street vacuums/motorbikes to pick up the dog poop because people somehow couldn't pick up their own. I was there again a couple years ago and didn't see any. Maybe their customs have changed?