Traditional Japanese tenkara fishers use unweighted flies. Most of the time, trouts like to hang out deeper in water. In order to fish with traditional flies, modern Japanese tenkara masters develop a technique to bring trouts closer to surface rather than using weighted flies. One of the techniques is hatch simulation which would fool the fish to think there is insect activity on the surface. This would trigger interest on the trout. It is a two step casting process.
A. Activity Simulation
Be sure fly is dry.
Cast about 4 -5 ft in front of the fish with a soft landing casting technique.
Repeat step 2 about 3 - 4 times.
B. Dead Drift
Soak fly wet and cast to the activity zone and let it drift towards the expecting fish.
Repeat a few times and move on if fish does not come up.
This technique is very useful for fishers who want to catch a specific fish they want. Fly fishing is all about fooling the fish.