Japanese cities tend to be very clean. It’s rare to see trash lying around.
The air quality also tends to be great. No holding your nose up when you exit a building (I’m looking at you, New York city).
Strangely enough there are also very few public trash cans. Consider this when you buy a coffee from a vending machine: it might be a while until you can dispose of the empty can. Look for can bins next to vending machines itself, or ask a convenience store or restaurant to put your trash in their “gomi bakku” (trashcan).