They do, indeed, but it is changing. I've been going to Japan since before 2000. Abruptly, right before the pandemic, in 2019, I started seeing trash. Even in the mountains! What kind of trash throws trash in the mountains?! I had a discussion with it with a local Australian who lived near my wife's parents' house and his wife (Japanese) blamed it on foreigners. He exploded and noted that there's even trash on the mountain behind their house (that's how I met them, incidentally, taking a photo of a flower by his house on the way back after a hike on that mountain) and no one hikes there except for locals (which is true), so it's not foreigners.
My wife said that due to the fear of terrorism, Japan removed all the public trash cans (I was confused -- didn't see the connection -- it was a fear of a terrorist placing a bomb in a rubbish bin), so that's why there's more trash, now. I said that would explain trash in the streets, but not trash in the mountains. And it's not just the local mountains, either. Even in the Minami Alps I'm finding trash.
On my last two visits (winter 2022 and summer 2023 -- making up for missed visits during the pandemic!), I didn't do any hiking 'cause I bought a bike and was biking instead. But, yeah, trash on the road in the countryside. It's not as bad as the US (I live on a nice street that's literally a block away from a very dangerous area -- gunshots, helicopters, police cars all the time) and I spend 1.5 hours per day at least 5 days a week picking up trash in the neighborhood. So, Japan is not nearly that bad -- Japan's "getting worse" is probably the same as "the best the US gets" -- but it's really disheartening to see trash on the streets and especially in the mountains, even if it's not at US levels. I mean this pretty much tells the story, really:
Speaking of Ohtani, here ya go! (they look the same in the previews, but the bottom photo is a much wider field of view -- now that I look a bit closer, I think the two preview photos are the same even the photos aren't! -- might be a bug)