Over 100 years ago, sea otters were hunted to the brink of extinction along Japan's coastline. But these adorably cute mammals are back and getting a welcome return in the northern prefecture of Hokkaido. Crowds line the cliffs of a remote cape to view 10 such creatures as they eat, care for their young and float on the water's surface as they sleep. But challenges remain. As their population increases, so will the effect on the area's marine resources, including clams, sea urchins and crabs.

A steady stream of tourists come to Yakushima Island each year to gaze up in awe at Japan's most famous tree. The Jomonsugi cedar exceeds 16 meters in circumference and is thought to be more than 2,000 years old. Is it the country's largest? And what lies up in the treetops hidden from view? The Darwin crew joined a special research team traversing the dense undergrowth in their four-year quest to locate other massive cedars and document the incredible ecosystem thriving in the tallest branches.