Walk off the main thoroughfares of Tokyo and you end up with plenty of grunge and grime, too. I got invited to step outside for a cigarette at a craft beer joint down an alley in Shibuya and our 3rd companion was a rat as large as any I'd ever seen in NYC. Plenty of trash in the alleys, kitchens dumping buckets of waste water and not caring if plenty splash over the street or sidewalk instead of going down the drain, etc.

It's impressive how well kept the main areas are, but any metro area of 40m people is gonna generate plenty of trash.