I've read that Japan had some crazy pollution and littering until regulations and campaigns in the 70s. Alright, I'll admit, I saw it on a Youtube short [1].
There doesn't seem to be a lot of information on the change on the Internet (at least not the English Internet), but this Japanese guy's anecdotes seem to corroborate it [2]. It makes sense, a lot of countries started taking pollution and littering more seriously around the 70s. It looks like that's when Japan started regulating it seriously [3]:
> from 24 November to 18 December 1970, 14 pollution control bills were passed into law [...] overnight, Japan was transformed from a country with meagre environmental regulations, to one of the strictest in the OECD.
1. https://www.youtube.com/shorts/PP60G-lMiDA