I lived in Taiwan, which also has a stagnant birth rate (only 181,606 births last year, https://www.taiwannews.com.tw/en/news/3611847) and a decades-long trend for young people to migrate to the large cities, or go to China to try their fortunes there.
But there is also a strong tradition of multi-generational households and traditions/holidays that emphasize family relations or filial piety, Lunar New Year being the most obvious. Certainly, family strife exists (and can be exacerbated if people are forced to live together) and many seniors live alone, but I think because of the cultural emphasis on familial contact, there is also a level of contact and awareness that can mitigate the extreme situations described in the article. Being smaller also helps (most cities on the island are no more than two or three hours away by high-speed rail).
In recent decades, there has also been a trend to legally allow foreign caregivers (mostly Filipinos and Indonesians) for people aged 85 and up, and tacitly allow for foreign caregivers for younger seniors and wealthy families. I am not sure how Taiwan's national health system covers those costs, or if the elderly poor can afford them.
Does Japan have any similar system of allowing foreign caregivers?