There are problems with the countryside in Japan; it's dying. It's the same old problem that happened in Europe in the early 19th century with the industrial revolution. Young people leave the farm and go to the cities to make money. The ones that are left are the old.
Here the story is one repeated thousands of times all over the rural areas of Japan.
The residents of a property have died, and the young have no use for their inheritance as it's worthless as noboby is around to buy it. They also might not declare themselves to be the inheritors and have to face property taxes. So the house falls into disrepair and eventually becomes a health hazard. The local authorities pull it down and it stays an empty space, with no value; a dead man's plot, as it's known. It's a sad situation but one that is also being repeated in some US cities like Detroit, I believe.