This technique is said to be able to break through any technique with a incrementally decreasing number of fingers in the form of knife hands. This is one of the Elder's 108 Special Techniques. The technique isn't simply reducing the number of fingers, as each strike with its particular number of fingers has a specific purpose for it.
The Elder mentions that he taught the technique to two men in the past: Kai Midō and Isshinsai Ogata. This is ironic in that the elder also saw Ogata's evil intentions and turned him away from Ryōzanpaku, though it could have been that he saw some purpose in attempting to reform Ogata from the Satsujinken through sympathy by teaching him a move that could void all defenses that he comes upon. There are three different variations of this technique, there is the Original Version used by Hayato, there is the Tenchi Mushin Style version used by Kai Midō and Tsutomu Tanaka, and the Ogata Style version used by Ogata Isshinsai. Each style appears to have its own level of intensity based on the skill and power of the user, and depending on the level of intensity, one style can completely eclipse the other style, as shown during the battle between Ogata and Tanaka.