The Japanese word for fly is "Kebari". Typically, this term is used in the English speaking world to describe a pattern originating in traditional Japanese Tenkara fishing. Many of these patterns are wet fly patterns, intended to be fished below the surface. Some Kebari are fished dry, and a few incorporate weights such as beads. Many Kebari are named after the regions where they were developed, and some are named after the master angler who developed them.
The Sakasa Kebari, or "Reverse Fly" is an iconic Tenkara pattern. Its most notable characteristic is that it is tied with a reverse hackle. Since the hackle faces the direction of the line, the angler can "pulse" the fly by twitching it back towards them. When twitched, it expands and flattens, and on a pause, it will contract and return to its original position. The resulting motions can be used to mimic the movements of insects in order to entice a strike.
If you are interested in exploring the history and development of Japanese Kebari, Yoshikazu Fujioka's website My Best Streams website is an excellent resource. Be sure to look over his Kebari History and Kebari Pattern PDFs.
Western Fly Patterns
You can get great results fishing typical Western flies on Tenkara, too! We really like fishing caddis imitations and think Tenkara is the perfect way to deliver a dry fly. Fishing nymphs on Tenkara is incredibly effective. Tenkara really lends itself to a nice presentation and a drag free drift, and keeping your line off the water. Competitive fly fishermen typically use a very long rod, a short section of fly line with a long leader and a nymph pattern. Sound familiar? We enjoy surprising amounts of success fishing streamer patterns (#8 and smaller) with Tenkara as well. Bottom line - don't be afraid to experiment with western flies on Tenkara!