Onsen: dive into another side of Japan

I’m hovering starkers beside a hot spring, or onsen, in a faded resort in southern Japan, while the Japanese grandmother standing naked next to me explains the form for the steaming pool I am about to enter. It’s an open-air mud hot spring, known as a doroyu and quite unusual, even in Japan, where the hyperactive geology means onsen of all kinds spring up — literally — everywhere.

I love a scalding bath, so it was perhaps inevitable that I should love onsen from the moment I first dipped a toe in one many years ago, close to Mt Fuji on a day trip from Tokyo. The ritual of washing before bathing, soaking in piping hot waters, the tranquillity, the beautiful settings, the deep sense of relaxation — I simply can’t get enough. Which is how I ended up in the city of Beppu — my first stop on a circumnavigation of the island of Kyushu in search of hot springs.

Kyushu is the most southerly of Japan’s four main islands. Its gateway city, Fukuoka, is five hours from Tokyo by the fastest bullet train, is famous for its ramen noodles and recently got its first Michelin guide and direct flights to Europe, thanks to KLM.

South-east of Fukuoka is Beppu — a paradise for hot-spring lovers and the obvious place to start an onsen odyssey. The city has everything from open-air baths known as rotenburo (I recommend Ichinoide Kaikan in the hills overlooking the city) to Japanese-style sauna-cum-steam-baths called mushiyu. Visitors also come to see the hot-spring ‘hells’, which are scalding, sulphurous and not for bathing in.

And it was next door to the touristy Monk’s Hell — where pools of thermal mud rise up from the ground in bubbles that resemble a monk’s tonsure — that I found the tiny, heavenly mud hot spring, Koudei Onsen.