They'll cave in within a few decades at most. I had a look at some comparative national statistics. There is also a growing number of LDP politicians who are pro-multicult (and the opposition parties are practically all more pro-multicult than the LDP).

Trust in government is down in the high 30's. Meanwhile, even dysfunctional India has 70% and even Canada and Sweden are in the high 40's. Note that America in 2017 is in the high 10's, having first reached this abysmal state as early as 1994. Another source, however, puts America in 2018 as instead being in the low 30's. China dominates the ranking at the mid 80's.

National pride in Japan is also at around 60%. Again, even putrid shitlib countries are exceeding it, e.g. Germany in the low 70's.

The only common potential determinant I can see here is left-liberalism. If multicult (effectively subordinate to left-liberalism) was the determinant, then Japan would be outperforming all of the multicult/heterogeneous shitholes because it combines liberalism with homogeneity. Instead, comparatively conservative countries like Poland, Turkey and India dominate both the national pride and trust in government rankings. Obviously countries combining liberalism and heterogeneity are averagely doing poorly on these statistics.

The "tl;dr" is that Japan was screwed over by having left-liberal ideology forcibly imposed on it by the Americans in the postwar period. To be precise, liberalism did, however, make earlier inroads, but was heavily repressed along with its offshoots like Marxism by the military regime. It was effectively impossible to have been an open Marxist or liberal in Japanese academia at that time. Fast forward to the 1980s and Japanese academia is already dominated by outright postmodernism (replacing Marxism which was very powerful in 1970s Japan). Given how superior Polish society is compared to today's Japan, Japan honestly would have done better to have been occupied by the USSR. They'd have suffered more economically in the short term, but in the long term less socially.