This is also sometimes called a Falcon’s Talon, although there are some subtle differences between these two strikes. The Nihon Nukite Tsuki is essentially a two finger poke or spearing action. The index and middle fingers are spread, extended and bent slightly (to prevent injury) while the remainder of the fingers and thumb are tucked into the palm of the hand. The tips of the fingers are used as the striking surface.
Falcon’s Talon is very similar, except that the thumb is also extended and bent slightly. In this way the thumb might be used to exert leverage in the target area helping the fingers be more penetrative or injurious. A possible scenario where this might apply is when the fingers strike the eyes and the thumb grasps under the chin. The thumb offers increased leverage for the fingers. This strike has limited uses and is generally used only when extensive damage to the target area is warranted.