Japan is a terrible place with a wonderful face. Then again, what place isn't to the disconnected observer...
Do bear in mind that from what I've read, even the 1990s was a
wild improvement over how it
used to be. One of the things I found very quickly was a paper on "Perception of mental illness and disability in Japanese society" (from the University of Iceland in 2020) where according to their citations, up until the 1950s or so (!) if you were a poor household who had a family member who was disabled to the point you found it difficult to look after them, it was legal - even arguably accepted/encouraged - to just... chain them up in a separate room that was all too often effectively a cage where they'd sit in their own filth all day.
The paper argues that this stemmed from animist beliefs about how once evil spirits started making somebody act "funny" like this, why, there was pretty much nothing you could do, and you just had to lock them up out of the way so they didn't pose a threat to the safety of the collective (the village or neighbourhood or whatever). This is supposedly the kind of thing that... mutated? into attitudes like Mii's grandmother, over time, the idea that people like this weren't just The Other, they were so different they were
scary, and a sign something was
deeply wrong. And that not only did "you" believe this, you knew (or you assumed) everybody else believed this too.
None of which is to remotely excuse these ideas and superstitions sticking around, obviously, or to argue Japan doesn't still have a problem with this stuff. But it
has changed, over time. Some of the families who had relatives killed in the Sagamihara Massacre did actually change their minds about keeping quiet and came forward to say no, such-and-such a person who died was my son, daughter, whatever, they existed, we did care about them, and they publicly stated on news programmes "We're doing this because we thought to act like it's shameful the way everyone usually does would be wrong".
I feel fairly sure the mangaka would agree things still aren't great, and I'm assuming she wouldn't want readers to go "Oh, I guess this character or that character can't be blamed
really". At the same time I don't think she'd want the takeaway to be "Life for disabled people in Japan is/was A LIVING HELL" or whatever. We've seen Muu-chan find happiness, of a sort, and we can see
some people in 2012 - other than Yamada - are willing to treat Mii-chan like a person
sometimes (...when it suits them), when they're much less likely to in the 1990s. (Chapter 12 makes that even clearer.)
I feel like it's more a story about how unlike Muu-chan, nobody ever stepped forward to clearly and unmistakeably say to Mii "Do you want help" - there's various reasons nobody does this, obviously (they're bigoted, they want to take advantage of her) but even the "good guys" arguably have the preconception she wouldn't be smart enough to take it. Even Suzaki fumbles this, really, with her "Oh crap this is too complicated", even if you can't blame her for not realising Mii-chan's mother had already primed her to see that as a sign of rejection. (And she is still trying in Chapter 12, too.)
Anyway, I'll, uh, stop typing essays, I guess. <_< Just wanted to get that off my chest. Again, I really didn't want to do this and have anyone thinking it's a "Japan = intrinsically bad" story, so I feel like I ought to go the extra mile to make that clear.