Seiyo stands at the western edge of the huge Shikoku Karst. Beneath this limestone plateau are numerous caves. One of these is in Shirokawa, a short distance from the main road. It’s called Anagami, the “Hole God”. In the ancient past, our human ancestors lived in the cave, but now it’s home to a legion of horseshoe bats.

The entrance to the cave is an aluminium door of the type seen on suburban homes. Next to it stand a middle-class Jōmon period couple dressed in deerskin. To enter the cave, you must go a little up the hill, cross the stream and call on the nearest white concrete house. The elderly lady will call a relative who will arrive shortly in a car bearing a key. This relative opens the door in the hillside, clicks on a light switch, and ushers you into the cave, promising to return in about half an hour.

Inside, the cave is a steady 14 degrees centigrade year round. A wet and slippery metal staircase goes up through a narrow tunnel that leads to a series of fantastic orifices in the rock. In the warmer months, the cave is alive with the sound of bats. You can hear their wings flapping, the sound getting quite loud as they approach your face. You can also hear them squeaking and clicking as they flit in and out of side passageways. They appear to respond to human clicks and whistles. The sound of water dripping and trickling echoes everywhere. In winter, the bats are hibernating, and you can see them up close, hanging from the ceiling, swaying gently in their sleep.

As with caves everywhere, there are numerous interestingly-shaped rock formations which have been given fanciful interpretations and labelled “Goddess”, “Stone Waterfall” and the like.

Spending time in the belly of the earth in close proximity to flying creatures is an exhilarating experience. If you’re prone to claustrophobia this may not be for you. The cave describes a torturous route in a generally upwards direction towards an opening higher up the cliff that overlooks the river. There’s no wheelchair access here, nor is it suitable for those with bad backs who are unable to stoop at unaccustomed angles.