Behind the hot spring village of Matsunoyama, up a flight of stone steps that disappear entirely under snow each winter, stands a small temple hall. From its grounds, once a year, men who married during the previous twelve months are thrown off the edge onto a five-metre slope of snow.

The explanations offered locally are not flattering. One holds that the custom began as revenge by young men whose village girls had been taken by outsiders. Another traces it to the residue of marriage by abduction. Neither story is told with much embarrassment, and neither has been tidied up.

Three hundred years of repetition turned it into a blessing. Grooms are now recruited nationally; applications close at the end of November, and couples arrive from Tokyo and Osaka for the privilege of being flung into a snowbank.

What follows is worse and better. A straw tower is burned, its ash mixed with snow, and the resulting black paste smeared across the face of everyone present, strangers included, with the word omedeto. It does not wash off with a towel.

Which is the point. Matsunoyama's water is so dense with ancient sea salt that it was once boiled down for salt itself, and people have travelled to it for healing for centuries. The ceremony survived here, and only here, because there was somewhere afterwards to go and get clean.