YOKOSUKA, Japan — Ever since her elderly neighbor moved a decade ago, Yoriko Haneda has done what she can to keep the empty house she left behind from becoming an eyesore. Ms. Haneda regularly trims its shrubs and clips its narrow strip of grass, maintaining its perfect view of the sea.

The volunteer yard work has not extended to the house two doors down, however. That one is vacant, too, and overgrown with bamboo. In fact, dozens of houses in this hillside neighborhood about an hour’s drive from Tokyo are abandoned.

“There are empty houses everywhere, places where nobody’s lived for 20 years, and more are cropping up all the time,” said Ms. Haneda, 77, complaining that thieves had broken into her neighbor’s house twice and that a typhoon had damaged the roof of the one next to it.

Despite a deeply rooted national aversion to waste, discarded homes are spreading across Japan like a blight in a garden. Long-term vacancy rates have climbed significantly higher than in the United States or Europe, and some eight million dwellings are now unoccupied, according to a government count. Nearly half of them have been forsaken completely — neither for sale nor for rent, they simply sit there, in varying states of disrepair.