A waterfall on Iriomote Island
Yusuke Okada/Getty Images

I rise at dawn for Yonna Deep Breathing, a yoga course on the beach that begins as the sun ­cautiously peers out over the horizon. Senses freshened, I fuel myself at the Hoshinoya restaurant with an inventive farmer’s breakfast, comprising a zesty pot-au-feu, pig trotters and marinated tuna, after which I hastily head for the harbor.

Kayaking on Iriomote with Pinaisara Fall in the distance
Ippei Naoi/Getty Images
Small ferries zip among the islands with regularity, with Ishigaki Ferry Terminal as the main hub. Forty minutes transport me to Iriomote, the largest island of the Yaeyamas and perhaps Japan’s most beguiling anomaly. A single coastal road exists, yet fails to encircle the 112 square miles of Iriomote, 90 percent of which is dense tropical rain forest and mangroves. I came ­prepared with basic protective gear for hostile wilderness; Iriomote hosts it in spades. It’s early afternoon during a typhoon season, immediately following a mammoth storm that kindly whisked away the clouds to allow a view of the bright blue skies. A light trek to Naara Falls seems like a harmless first hike — and a naturalist’s delight, given the abundance of tree-climbing lizards and oversized insects lining the rugged route. Picturesque Pinaisara Fall may be Okinawa’s tallest, at 180 feet but, with a natural diving pool at Naara’s base, it is the explorer’s proverbial holy grail.

On my return to port, I trade land for water, navigating through mangroves using a kayak and an oar, which local hotels are only too keen to provide. Among entwined roots and thickets, I encounter the odd paddling passerby, greeting them with the obligatory konnichiwa (good day).

It’s in darkness, though, that this dense jungle island truly inspires the intrepid. I replace my sandals with Wellingtons, trade my tank top for long sleeves and bear a ­heavy-duty flashlight. A good 80 percent of the land here is protected, and its inhabi­tants attempt to reclaim the remainder once the sun’s gaze is turned elsewhere. Roads become thoroughfares for palm-tree crabs and snakes, one of which, the habu, is venomous, with a fatality rate of around 3 percent. I, however, am out on a cat-watching mission. The Iriomote wildcat (known locally as the yamaneko) is the island’s most eminent resident. With only about 100 of the small leopard subspecies remaining, the gray-and-brown feline is critically endangered. It takes luck and judgment to catch a glimpse.