I am actually curious what is the solution you're talking about, unless you mean hardcore immigration that's most of the west using as a stopgap. I have no problem with it, but don't think it actually resolves the problem long-term.
Based on the animation above, a half century out, 2070; the demographic disparity is significantly less pronounced in Japan.
From a US perspective going from 3.62 avg children to replacement rate (2) is much more severe than going from 2 to 1.73.
*Though, this data does put an interesting perspective on european immigration and the great depression from 1910-1930. From replacement rates, 4.24 (1880) to 2.22 (1940)
https://populationeducation.org/wp-content/uploads/2020/04/a...
The rest of us of course wouldn't know how to handle uneducated migrating masses.
This would require not only legislative changes, but also a significant social shift. The broad Japanese society simply does not believe at present in “assimilation”, because it maintains such a strict in-group, out-group separation and the latter simply can never be Japanese in their view. For example, up to the end of the 20th century, Japanese would trust foreigners less the better those foreigners spoke Japanese, because a truly fluent and proficient foreigner would be viewed as confused about his/her ethnic identity or trespassing on something distinct Japanese. This has gradually changed somewhat with the influx of people from other Asian countries who work in kombinis etc., but it still shows the sort of social resistance that advocates for immigration reform are up against.
I have no idea how to get people to have kids though. Some things like child care, time off for kids, and different taxes can be tried, but are they enough?
When you think about it, it really seems like a gigantic task
USA ships them to Mexico in exchange for cheap labor