First - cultures will be cultures. They can change over time, but it usually isn't a fast process.
Also, they aren't monolithic, so it's not like "this is how Japan is", but rather "this is a facet of how things might be viewed in some Japanese circles".
I would recommend 3 films by Yasujiro Ozu, one of Japan's greatest film makers, the "Noriko trilogy" (starring
Setsuko Hara):
Late Spring (1949),
Early Summer (1951) and
Tokyo Story (1953)
They all discuss societal change (after WW2, but not just), with people moving to the cities, weakening ties between generations (daughters maybe choosing their own lives, rather than staying to take care of an elderly parent), and so on.
They side with the conservative view that looks at the positive sides of familial ties, close knit social fabrics in villages, and so on - quite seducing, if you aren't aware of what the director is doing. Especially since he
does show that those old ways are removing choice for the younger generation,
and those gaining from them (old father, etc) are depicted as feeling they are unfair burdens, etc. So you don't get as clear negatives as in this manga ...
Fantastic films, but one needs to be aware, and not just absorb the message.
AND they are relevant to this manga, since it does have the themes of how we as a society, whether it be as families, friends, fellow men, or maybe "village", "city", or "country/civilization/culture", handle crises, where people hurt, and need help.
These are worthy subjects of discussion for a society. THIS is (one of) the great reasons for all forms of culture.
The potential changes, whether slow or fast (the above is clearly still going on in Japan) need discussion.
And we are part of it right now, right here.

So let's be kind to one another - but also straight, true, and clear, if you ask me.