Japan is very similar but not exclusive to parks, even in the middle of Tokyo. Pretty much EVERYWHERE in Japan expects you to carry your own trash.
The only exception to this really being at restaurant’s, street food markets, and “some” vending machines (which will have recycling for cans/plastic).
And you know what? There’s very little trash on the streets. The dirtiest areas I experienced was Osaka near Amerika-mura (young trendy area) which was mostly just stuck gum, cigarette butts, and in the early AM maybe an empty can of beer.
You obviously didn’t read the article.