You stumble across them everywhere, in villages and cities, in the smartest neighbourhoods and the most run down. They lurk behind overgrown gardens, decaying beneath veils of moss and ivy. Crows and raccoon dogs make their homes in them; little children peer through their gates and imagine ghosts. They are the “witch houses” of Japan — mysterious tokens of social decay in one of the wealthiest societies in the world. Called akiya, or abandoned homes, they have spread like mould in the past few years. The last time the government made a count, five years ago, it found 8.5 million...