Below I quote a passage from the 30th essay of “Essays in Idleness,” the writings of a monk named Kenkō, translated by Donald Keene.

As long as people remember the deceased person and miss him, all is still well, but before long those people too disappear, and the descendants, who know the man only from reports, are hardly likely to feel deep emotion. Once the services honoring the dead man cease, nobody knows who he was or even his name. Only the sight of the spring weeds sprouting each year by his grave will stir the emotions of sensitive people; but in the end, even the pine tree that groaned in the storm winds is broken into firewood before it reaches its allotted thousand years, and the old grave is plowed up and turned into rice land. How sad it is that even this last memento of the dead should vanish.

I suppose that’s just the way of these things. After this point is the true death, although even Genghis Khan was buried in an unmarked grave and certainly nobody remembers him alive.