"Oh, if you want to pee you can just do it out the front door," my host Yuki says as he gives me an introductory tour of the house and points out the powder room — merely a pit with a long drop and an unconnected toilet pedestal covering the hole.

I had just arrived with a friend named Henry on the island of Yakushima, which lies in the East China Sea about 190 km south of Kagoshima in Kyushu. It is famed for its wild virgin forests, including many specimens of yakusugi (Yakushima cedars more than 1,000 years old), amazing wildlife and dramatic coastlines — but it also rains a lot: 35 days a month, or so the saying goes. The day we arrived at this outpost of Kagoshima Prefecture was no exception, and there were two more days of torrential downpours forecast.

So, come rain but no shine, I had embarked on my debut "couch-surf" — courtesy of CouchSurfing.com. Over the past eight years since it was set up, this not-for-profit enterprise has come to be well known in the backpacking community; indeed, it has become something of a phenomenon.